When you need synonyms for investigated, the best replacement depends on what kind of investigation took place. A detective may examined evidence, a researcher may have studied a subject, an employer may have looked into a complaint, and a scientist may have analyzed data. These words are related, but they are not always interchangeable.
Choosing the right alternative can make your writing more precise and natural. This guide explains formal, neutral, professional, academic, legal, and casual alternatives to investigated, along with examples, grammar tips, sentence transformations, email examples, and practical guidance for choosing the right word.
Quick Answer
Common synonyms for investigated include examined, researched, studied, analyzed, explored, reviewed, assessed, inspected, scrutinized, evaluated, looked into, inquired into, probed, and examined closely. The best choice depends on context: analyzed suits data, examined suits evidence, researched suits academic work, and looked into suits everyday communication.
Quick List: Synonyms for Investigated
Closest and Most Useful Alternatives
- Examined
- Studied
- Researched
- Analyzed
- Reviewed
- Explored
- Assessed
- Inspected
- Scrutinized
- Evaluated
- Inquired into
- Looked into
- Probed
- Examined closely
- Investigated thoroughly
Formal Alternatives
- Examined
- Analyzed
- Assessed
- Evaluated
- Scrutinized
- Inquired into
- Conducted an inquiry into
- Conducted an examination of
- Researched
- Reviewed
Neutral Alternatives
- Studied
- Looked into
- Reviewed
- Explored
- Checked
- Examined
- Researched
- Assessed
Casual Alternatives
- Looked into
- Checked out
- Dug into
- Checked
- Looked over
Formal Alternatives for Investigated
Examined
Meaning: Looked at something carefully to understand or evaluate it.
Explanation: Examined is one of the closest alternatives to investigated. It suggests careful inspection but does not necessarily imply wrongdoing or a formal investigation.
Example: The committee examined the evidence before making its decision.
Best Use: Reports, academic writing, workplace communication, and evidence-based discussions.
Worst Use: Avoid it when you specifically need to communicate that an official criminal or legal investigation took place.
Tone: Formal and neutral.
Analyzed
Meaning: Studied something carefully by breaking it into parts.
Explanation: Analyzed emphasizes detailed examination, especially of information, data, evidence, or results.
Example: The researchers analyzed the survey responses.
Best Use: Academic, scientific, technical, and business writing.
Worst Use: It may sound inaccurate if someone simply inspected an object without studying its details.
Tone: Professional and analytical.
Assessed
Meaning: Judged or evaluated something after careful consideration.
Explanation: Assessed focuses more on determining condition, value, risk, quality, or significance than on discovering facts.
Example: The safety team assessed the risks associated with the equipment.
Best Use: Risk reports, education, business, healthcare, and professional evaluations.
Worst Use: Do not use it when the main action was searching for evidence of an unknown event.
Tone: Formal and professional.
Evaluated
Meaning: Carefully judged the quality, effectiveness, importance, or value of something.
Explanation: Evaluated is related to investigated, but it usually implies that the investigator reached a judgment or assessment.
Example: The panel evaluated the proposal before approving it.
Best Use: Business, education, research, performance reviews, and policy discussions.
Worst Use: It is not always suitable when the investigation was purely fact-finding.
Tone: Formal and professional.
Scrutinized
Meaning: Examined something extremely carefully.
Explanation: Scrutinized emphasizes close attention to detail. It can suggest that the subject was examined because there were questions, concerns, or possible problems.
Example: Auditors scrutinized the company’s financial records.
Best Use: Financial reports, investigations, journalism, and formal criticism.
Worst Use: It can sound overly intense for a routine review.
Tone: Formal and strong.
Inquired Into
Meaning: Sought information about something, often through a formal process.
Explanation: This phrase can replace investigated when the focus is on asking questions or gathering information.
Example: The board inquired into the circumstances surrounding the incident.
Best Use: Formal reports, official inquiries, and institutional writing.
Worst Use: It may sound unnatural in casual conversation.
Tone: Formal.
Conducted an Inquiry Into
Meaning: Carried out a formal investigation or examination.
Explanation: This is a useful alternative when you want to emphasize an organized or official process.
Example: The committee conducted an inquiry into the reported safety concerns.
Best Use: Government, corporate, academic, and institutional writing.
Worst Use: It is unnecessarily formal for a simple everyday check.
Tone: Very formal and official.
Conducted an Examination of
Meaning: Carried out a detailed review or inspection.
Explanation: This phrase emphasizes the process of carefully studying something.
Example: The auditors conducted an examination of the company’s financial records.
Best Use: Formal reports, audits, academic writing, and professional documents.
Worst Use: It can sound bureaucratic in ordinary conversation.
Tone: Formal.
Researched
Meaning: Gathered and studied information about a subject.
Explanation: Researched is appropriate when the investigation involves collecting information from sources, studies, records, or observations.
Example: The journalist researched the company’s history before writing the article.
Best Use: Academic work, journalism, business research, and general information gathering.
Worst Use: It may not accurately describe a police investigation or a brief inspection.
Tone: Neutral to formal.
Reviewed
Meaning: Examined something carefully, often to check, assess, or understand it.
Explanation: Reviewed is broader and usually less intense than investigated.
Example: The manager reviewed the complaint before responding.
Best Use: Emails, workplace reports, documents, applications, and internal processes.
Worst Use: It may be too mild when a serious formal investigation occurred.
Tone: Professional and neutral.
Semi-Formal and Neutral Alternatives
Studied
Meaning: Gave careful attention to something to learn or understand it.
Explanation: Studied is a broad alternative that works well when the purpose was understanding rather than uncovering wrongdoing.
Example: Scientists studied the effects of the new treatment.
Best Use: Academic, scientific, educational, and everyday contexts.
Worst Use: It can sound too general for a formal criminal inquiry.
Tone: Neutral.
Explored
Meaning: Examined a subject or possibility in detail.
Explanation: Explored often suggests looking at different aspects, possibilities, or explanations.
Example: The researchers explored several possible causes of the problem.
Best Use: Research, brainstorming, academic writing, and analytical discussions.
Worst Use: Avoid it when you need to emphasize an official investigation.
Tone: Neutral to professional.
Looked Into
Meaning: Investigated or tried to find out more about something.
Explanation: Looked into is one of the most natural conversational alternatives to investigated.
Example: The manager looked into the customer’s complaint.
Best Use: Emails, workplace conversations, customer service, and everyday English.
Worst Use: It may be too casual for a highly formal legal document.
Tone: Neutral and conversational.
Inspected
Meaning: Examined something closely to check its condition or quality.
Explanation: Inspected is narrower than investigated. It usually involves physically checking something or systematically checking a place, object, or system.
Example: The engineer inspected the building for structural problems.
Best Use: Safety checks, property, equipment, manufacturing, and inspections.
Worst Use: It is not a natural replacement for every investigation involving people or events.
Tone: Professional and neutral.
Checked
Meaning: Looked at something to make sure it was correct, safe, or acceptable.
Explanation: Checked is much less formal and less intense than investigated.
Example: The technician checked the system for errors.
Best Use: Everyday conversation and routine workplace communication.
Worst Use: Avoid it when describing a serious or extensive investigation.
Tone: Casual to neutral.
Evaluated
Meaning: Considered something carefully to judge its quality or effectiveness.
Explanation: This works when the investigation involved making a judgment.
Example: The company evaluated the results of the trial.
Best Use: Business, education, research, and professional assessments.
Worst Use: It may not fit a fact-finding investigation where no judgment was made.
Tone: Professional.
Reviewed
Meaning: Looked at something carefully, often to determine whether action is needed.
Explanation: This is particularly useful in workplace writing because it sounds professional without sounding overly dramatic.
Example: The HR department reviewed the complaint.
Best Use: Workplace communication, policies, complaints, and documents.
Worst Use: It may understate the seriousness of a major investigation.
Tone: Neutral and professional.
Considered
Meaning: Thought carefully about something.
Explanation: Considered is broader and weaker than investigated. It focuses on thinking about an issue rather than actively gathering evidence.
Example: The committee considered several explanations for the delay.
Best Use: Decision-making and general discussions.
Worst Use: Do not use it if you need to show that evidence was actively collected.
Tone: Neutral.
Informal and Casual Alternatives
Looked Into
This is the most useful casual alternative.
Example: I looked into the issue and found that the file had been moved.
Natural when: Speaking with coworkers, friends, customers, or acquaintances.
Avoid when: Writing highly formal legal or academic documents.
Tone: Conversational and professional enough for many workplace situations.
Checked Out
Meaning: Examined or investigated something informally.
Example: I checked out the issue and found a simple explanation.
Natural when: Casual conversation.
Avoid when: Writing formal reports or communicating serious findings.
Tone: Casual.
Dug Into
Meaning: Investigated something deeply or in detail.
Example: The reporter dug into the company’s financial records.
Natural when: Informal discussions and journalism-related conversation.
Avoid when: Writing highly formal documents.
Tone: Casual and vivid.
Looked Over
Meaning: Examined something quickly or generally.
Example: I looked over the documents before the meeting.
Natural when: Describing a brief review.
Avoid when: The work involved an extensive investigation.
Tone: Casual and neutral.
Checked
Meaning: Examined something briefly to find out whether there was a problem.
Example: The mechanic checked the engine for unusual sounds.
Natural when: Routine situations.
Avoid when: The investigation was detailed or official.
Tone: Casual and neutral.
True Synonyms vs. Contextual Alternatives
Not every word in the list above can replace investigated without changing the meaning.
| Type | What It Means | Can It Replace the Original? |
|---|---|---|
| True synonym | A word with essentially the same core meaning | Usually |
| Near synonym | A word with a closely related meaning | Sometimes |
| Contextual alternative | Works in a particular situation | Depends on context |
| Broader expression | Has a wider or less specific meaning | Sometimes |
| Narrower expression | Describes one specific kind of investigation | Only in suitable contexts |
For example, examined is often very close to investigated, while assessed emphasizes judgment. Inspected usually involves checking something systematically, while researched emphasizes gathering information.
Similarly, looked into can replace investigated in everyday speech, but it is less formal. Scrutinized suggests unusually close examination and may imply concern or suspicion.
Industry-Specific Usage
Business Writing
Business writing usually benefits from precise and neutral alternatives.
Useful choices include:
- Examined
- Reviewed
- Analyzed
- Assessed
- Evaluated
- Looked into
Example:
“The finance team analyzed the quarterly figures to identify the source of the discrepancy.”
This sounds more precise than simply saying the team “investigated the figures.”
Corporate Communication
Corporate communication often needs language that is clear without sounding unnecessarily alarming.
Example:
“The company reviewed the reported concern and is taking appropriate steps to address it.”
Here, reviewed may be preferable to investigated when the organization wants to describe a review without suggesting a particular conclusion.
For a formal internal report:
“The committee conducted an inquiry into the reported incident.”
Academic Writing
Academic writing often uses:
- Examined
- Studied
- Analyzed
- Explored
- Evaluated
- Researched
- Assessed
Example:
“This study examined the relationship between sleep patterns and academic performance.”
Use analyzed when discussing data:
“The researchers analyzed responses from the participants.”
Use explored when examining a topic, idea, or possible relationship:
“The study explored possible reasons for the decline.”
Customer Service
Customer service language should be clear and reassuring without making promises that have not been verified.
Useful choices include:
- Reviewed
- Looked into
- Checked
- Examined
Example:
“We have reviewed your account and identified the source of the issue.”
For a less formal response:
“I’ll look into this for you and get back to you with an update.”
Legal Writing
Legal contexts require particular care because investigated, examined, inquired into, and related terms can have different implications depending on the document and jurisdiction.
For example:
“The agency investigated the allegations.”
is not necessarily identical in meaning to:
“The agency reviewed the allegations.”
The second statement may describe a less extensive process.
In formal legal or regulatory writing, use the terminology that accurately describes the documented process rather than choosing a synonym simply because it sounds more sophisticated.
Email Communication
Professional emails commonly use reviewed, looked into, examined, or investigated, depending on the seriousness and nature of the matter.
For example:
“We have reviewed your request and will provide an update shortly.”
For a more serious matter:
“Our team has investigated the reported issue and identified the cause.”
Email Examples
Client Communication
Subject: Update on Your Reported Issue
Email① Original② Write Like MeUpdate on Your Reported Issue
Update on Your Reported Issue
Hello Sarah,
We have reviewed the issue you reported and confirmed that the delay was caused by an error during processing.
Our team has corrected the problem, and your request is now moving forward. We appreciate you bringing this to our attention.
Best regards,
Michael
Project Update
Subject: Project Review Completed
Email① Original② Write Like MeProject Review Completed
Project Review Completed
Hi Daniel,
I’ve reviewed the project records and compared the latest figures with the previous report.
I found two differences that need to be corrected before we finalize the document. I’ve marked both items for your review.
Best,
Emily
Internal Workplace Email
Subject: Update on the Reported Concern
Email① Original② Write Like MeUpdate on the Reported Concern
Update on the Reported Concern
Hi Team,
The management group has looked into the concern raised yesterday. We are still reviewing a few details and will share additional information once the review is complete.
Thank you for your patience.
Regards,
James
Customer Service
Subject: Your Support Request
Email① Original② Write Like MeYour Support Request
Your Support Request
Hello,
We have examined the information associated with your support request and identified the source of the problem.
The necessary correction has been made. Please let us know if you continue to experience the issue.
Kind regards,
Customer Support Team
Academic Communication
Subject: Research Findings
Email① Original② Write Like MeResearch Findings
Research Findings
Dear Professor Lee,
I have analyzed the survey responses and identified several patterns that may be relevant to the research question.
I have included the findings in the attached report and highlighted the areas that may require further discussion.
Best regards,
Alex
Short Dialogue Examples
Workplace
Person A: Did you investigate the missing invoices?
Person B: Yes. I reviewed the records and found that they were filed under a different project.
Classroom
Person A: What did your group study?
Person B: We examined how different study environments affected concentration.
Customer Service
Person A: Has anyone checked my order?
Person B: Yes, I looked into it this morning. It is currently being processed.
Casual Conversation
Person A: Did you find out why the computer stopped working?
Person B: Yeah, I dug into it and discovered that the update caused the problem.
Professional Discussion
Person A: What did the committee discover?
Person B: They analyzed the available evidence and identified several inconsistencies.
How to Replace “Investigated” in a Sentence
Example 1
Original:
The researchers investigated the effects of the new treatment.
Alternative:
The researchers examined the effects of the new treatment.
Why it works:
Examined sounds natural in academic writing and preserves the idea of careful study.
Example 2
Original:
The team investigated the customer complaint.
Alternative:
The team reviewed the customer complaint.
Why it works:
Reviewed sounds professional but may imply a less extensive process than investigated.
Example 3
Original:
The scientists investigated the test results.
Alternative:
The scientists analyzed the test results.
Why it works:
Analyzed is more precise when the scientists examined detailed results or data.
Example 4
Original:
The journalist investigated the allegations.
Alternative:
The journalist researched the allegations.
Why it works:
Researched emphasizes gathering information. It does not necessarily imply a formal investigation.
Example 5
Original:
The manager investigated the problem.
Alternative:
The manager looked into the problem.
Why it works:
Looked into is natural in everyday workplace communication and sounds less formal.
Example 6
Original:
The engineers investigated the damaged bridge.
Alternative:
The engineers inspected the damaged bridge.
Why it works:
Inspected is more specific when engineers physically examine a structure.
Example 7
Original:
The committee investigated several possible explanations.
Alternative:
The committee explored several possible explanations.
Why it works:
Explored works particularly well when considering different possibilities rather than conducting a formal inquiry.
Example 8
Original:
The auditors investigated the financial records.
Alternative:
The auditors scrutinized the financial records.
Why it works:
Scrutinized emphasizes extremely careful examination.
Example 9
Original:
The safety team investigated the risks.
Alternative:
The safety team assessed the risks.
Why it works:
Assessed focuses on judging the level or nature of the risks.
Example 10
Original:
The board investigated the circumstances surrounding the incident.
Alternative:
The board conducted an inquiry into the circumstances surrounding the incident.
Why it works:
The replacement creates a more formal institutional tone.
Comparison Table
| Phrase | Tone | Meaning / Scope | Best Use | Example |
|---|---|---|---|---|
| Investigated | Neutral/formal | Searched for facts or explanations | General investigations | The team investigated the issue. |
| Examined | Formal/neutral | Looked at carefully | Evidence, research, documents | They examined the evidence. |
| Analyzed | Professional | Studied details or data | Research and statistics | They analyzed the results. |
| Researched | Neutral/formal | Gathered information | Academic work and journalism | She researched the topic. |
| Reviewed | Professional | Looked over carefully | Documents and complaints | We reviewed the report. |
| Assessed | Formal | Judged condition, value, or risk | Risk and evaluation | They assessed the risks. |
| Evaluated | Formal | Judged quality or effectiveness | Business and education | They evaluated the proposal. |
| Scrutinized | Strong/formal | Examined extremely closely | Records and evidence | Auditors scrutinized the accounts. |
| Inspected | Professional | Checked condition carefully | Buildings and equipment | Engineers inspected the bridge. |
| Explored | Neutral | Considered possibilities or aspects | Research and ideas | The study explored possible causes. |
| Looked into | Conversational | Investigated or checked | Everyday and workplace speech | We looked into the complaint. |
| Checked | Casual/neutral | Made a basic examination | Routine issues | I checked the system. |
| Probed | Formal/strong | Investigated deeply | Serious issues and journalism | The committee probed the allegations. |
Which Alternative Should You Choose?
For Formal Writing
Choose examined, analyzed, assessed, evaluated, scrutinized, or inquired into, depending on the exact action.
For Business Communication
Choose reviewed, examined, assessed, analyzed, or looked into.
For Academic Writing
Choose examined, analyzed, studied, researched, or explored.
For Legal Writing
Use the exact term that describes the documented process. Investigated, inquired into, examined, and reviewed can carry different implications.
For Professional Email
Reviewed and looked into are often natural choices for routine matters. Use investigated when an actual investigation took place.
For Everyday Conversation
Looked into, checked, and checked out can sound natural.
For Casual Messages
Looked into or dug into may work when the situation is informal.
Grammar and Usage Guide
“Investigated” Is the Past Tense and Past Participle
The base verb is investigate.
- Present: The team investigates the complaint.
- Past: The team investigated the complaint.
- Present perfect: The team has investigated the complaint.
- Past perfect: The team had investigated the complaint.
- Passive: The complaint was investigated by the team.
“Investigate” Usually Takes an Object
You can say:
The police investigated the incident.
You can also use:
The police investigated the cause of the incident.
Avoid adding an unnecessary preposition such as investigated about.
“Investigate Into” Is Usually Incorrect
In standard English, use:
The committee investigated the matter.
or:
The committee inquired into the matter.
The construction investigated into the matter is generally not standard.
“Investigated” Can Be Used in Passive Sentences
For example:
The complaint was investigated by the department.
This structure is common in formal and professional writing.
“Investigated” Does Not Automatically Mean “Proved”
An investigation means that someone examined an issue or sought facts. It does not necessarily mean that the investigation confirmed wrongdoing.
Compare:
The company investigated the allegation.
with:
The company confirmed the allegation.
These statements do not mean the same thing.
Common Mistakes to Avoid
1. Treating Every Alternative as an Exact Synonym
Investigated, assessed, reviewed, and analyzed overlap, but each emphasizes something different.
2. Using “Researched” for Every Investigation
Research usually involves gathering and studying information. It does not always describe an official investigation.
3. Using “Inspected” for Abstract Issues
Inspected is especially natural for physical objects, locations, systems, or conditions.
4. Using “Scrutinized” for Routine Reviews
Scrutinized suggests very close examination. It can sound unnecessarily intense for ordinary work.
5. Making Casual Language Too Formal
“Conducted an inquiry into the issue” may sound excessive in a quick workplace message when “looked into the issue” would be clearer.
6. Making Serious Investigations Sound Too Casual
“Checked out the allegations” may be inappropriate for a formal report.
7. Confusing Investigation With Evaluation
An investigation seeks information or facts. An evaluation usually involves judging quality, effectiveness, value, or risk.
8. Using “Investigated Into”
Use investigated the issue, not investigated into the issue.
9. Assuming Investigation Means Proof
An investigation can uncover evidence, but the word itself does not say what the final evidence established.
When Not to Use “Investigated”
When You Only Performed a Routine Check
If you simply verified something, checked may be more accurate.
I checked the figures.
When You Reviewed a Document
If you simply read and considered a document, reviewed may be better.
The manager reviewed the proposal.
When You Analyzed Data
If you worked with detailed information or statistics, analyzed gives readers more precision.
The researchers analyzed the survey results.
When You Judged Quality or Risk
Use assessed or evaluated when the main purpose was judgment.
The team assessed the safety risks.
When You Physically Examined Something
Use inspected for many physical checks.
The engineer inspected the equipment.
When You Considered Possible Explanations
Use explored when you examined different possibilities.
The researchers explored several possible causes.
When You Want a Conversational Tone
Use looked into instead of investigated when appropriate.
I’ll look into the issue and let you know.
Advanced Writer Tips
Tone Control
Small word choices can change the tone significantly.
More conversational:
We looked into the problem.
Neutral:
We reviewed the problem.
More formal:
We conducted an inquiry into the matter.
Choose the level that fits your audience.
Professional Email Etiquette
Professional writing does not always need the most formal word available. A clear phrase such as reviewed the issue can sound more natural than a complicated expression.
Politeness
Indirect language can sometimes sound more considerate.
Compare:
We investigated your complaint.
with:
We reviewed the concern you raised.
The second version can sound less confrontational while still communicating that the matter received attention.
Context Alignment
Think about what was actually done before choosing a synonym.
If someone collected data, consider researched or analyzed.
Checked a physical structure, consider inspected.
If someone examined a complaint, consider reviewed or looked into.
Precision
The most sophisticated word is not necessarily the best word. Precision matters more than formality.
For example, analyzed is better than investigated when the specific action involved detailed analysis of data.
Readability
If your audience does not need formal language, choose a familiar word.
Instead of:
The committee conducted an examination of the matter.
you may simply write:
The committee examined the matter.
The shorter version is often clearer.
Related Questions
What is another way to say “investigated”?
Common alternatives include examined, analyzed, researched, studied, reviewed, assessed, explored, inspected, scrutinized, and looked into. The correct choice depends on what the investigation actually involved.
What is a professional alternative to “investigated”?
Reviewed, examined, analyzed, assessed, and evaluated are useful professional alternatives. Choose the one that accurately describes the action.
What is a formal alternative to “investigated”?
Depending on context, you can use examined, scrutinized, inquired into, conducted an inquiry into, or conducted an examination of.
What can I use instead of “investigated” in an academic paper?
Examined, analyzed, studied, explored, researched, and evaluated are common choices. Analyzed is especially useful for data, while explored works well for broader topics or possibilities.
Is “investigated” a formal word?
Yes. Investigated is neutral-to-formal and works in professional, academic, journalistic, legal, and everyday contexts. Its level of formality depends partly on the surrounding language.
Can I use “looked into” instead of “investigated”?
Yes, in many conversational and workplace contexts. Looked into is less formal and may sound inappropriate in highly formal legal or academic writing.
What is the difference between “investigated” and “analyzed”?
Investigated generally means searched for facts, information, or explanations. Analyzed means examined something in detail, often by breaking information or data into parts. An investigation may include analysis, but the words do not always mean the same thing.
FAQs
Is “examined” a synonym for “investigated”?
Often, yes. Examined is one of the closest alternatives, but it can be broader. It means looking at something carefully, while investigated often suggests an effort to discover facts or explanations.
Is “researched” the same as “investigated”?
Not always. Researched focuses on gathering and studying information, while investigated can involve evidence gathering, questioning, inspection, or fact-finding.
Is “looked into” too informal?
Not necessarily. It is common in everyday speech and professional emails. However, it is more conversational than investigated and may not fit formal reports.
What is the strongest synonym for “investigated”?
There is no single strongest synonym for every context. Scrutinized suggests especially close examination, while probed can suggest a deep investigation. The appropriate choice depends on the situation.
Can “reviewed” replace “investigated”?
Sometimes. Reviewed usually suggests examining information, documents, or a matter, but it may not communicate the full depth of a formal investigation.
What is the best synonym for “investigated” in academic writing?
Common academic choices include examined, analyzed, studied, explored, and researched. The best option depends on the research method and what the writer actually did.
What is the difference between “investigated” and “inspected”?
Investigated usually involves finding facts, causes, or explanations. Inspected usually means carefully checking a physical object, location, system, or condition.
Key Takeaways
- Investigated means examined something to discover facts, causes, or information.
- Examined is one of the closest general alternatives.
- Use analyzed for detailed study of data, information, or evidence.
- Use reviewed, checked, or looked into when a less formal or less intense expression is more accurate.
- Always choose the alternative that matches the actual action, tone, audience, and level of investigation.
Conclusion
The best synonym for investigated depends on exactly what happened. Examined is a strong general alternative, while analyzed is more precise for data and evidence. Researched emphasizes information gathering, reviewed suggests careful consideration, assessed focuses on judgment, and inspected works especially well for physical checks. In everyday and workplace communication, looked into is a natural conversational choice.
For formal writing, precision matters more than choosing the most complicated word. A serious inquiry may require investigated, inquired into, or conducted an inquiry into, while a routine document check may be better described as a review. Always consider what was actually done, who will read the sentence, and whether the replacement changes the meaning. The right alternative makes your writing clearer, more accurate, and more natural.