Workplace Incident Investigations Complete Guide

By Kathleen Clair, CSP, MS, SMS

The last thing a safety officer or company management wants to hear is that an accident has occurred in their workplace. On-the-job accidents can result in injuries to workers or costly damage to equipment or property.

According to the National Safety Council (NSC), the total cost of work injuries in 2019 was $171 billion. This number includes wage and productivity losses ($53.9 billion), medical expenses ($35.5 billion), and administrative expenses ($59.7 billion). The cost of a serious workplace injury or accident can gravely affect the bottom line of a company.

Ensuring that your company has an effective incident investigation program in place can help you learn from the accident and prevent a similar mishap from happening in the future.

how to conduct an incident investigation

Why Investigate Incidents and Near Misses?

Incident investigations are used to determine the cause of an incident, to identify unsafe conditions or acts, and to identify corrective actions so that similar incidents do not occur in the future. In other words, the goal of the investigation is to discover the root causes of the accident and prevent it from happening again.

The purpose of the investigation is prevention, not to place blame. According to the Occupational Safety and Health Administration (OSHA), incident investigations that focus on identifying and correcting root causes, not on finding fault, will also improve workplace morale and increase productivity by demonstrating an employer’s commitment to a safe and healthful workplace.

what incidents to investigate

The benefits of a successful accident investigation program includes:

  • Prevents future injuries and illnesses
  • Reduces the cost of losses
  • Demonstrates the company’s commitment to health and safety
  • Promotes positive workplace morale

What Events Should Be Investigated?

The following incidents should be investigated beginning with the most critical.


  • Serious injury or death
  • An injury requiring medical treatment
  • Minor injuries requiring first aid treatment
  • Minor injuries that have the potential serious injury
  • Near misses or close calls


  • Major structural failure or collapse
  • Major release of hazardous substances
  • Dangerous incident involving fires or explosive materials
  • Minor chemical spills
  • Near misses or close calls

Who Should be on the Investigation Team?

Incident investigations are frequently performed by supervisors or management. However, to be most effective, the investigation should include both management and general staff working as a team, since everyone contributes different knowledge, understanding and perceptions to the investigation. The investigations should be conducted by people who know the work area, the actual work process, and the equipment if applicable.

incident investigation training

When conducting an investigation, the team must dig deeper than the immediate and obvious causes of the incident. Simply concluding that “carelessness” or “employee failed to follow a procedure” was the cause of an incident is not sufficient.

This lack of in-depth analysis fails to discover the root causes of the incident and will not identify the overall changes and steps that are necessary to prevent future incidents. When a deficiency is recognized, it is important to examine why it existed and why it was not previously identified or addressed.

Training for Conducting Investigations

Employees who participate in incident Investigation should receive training on the following:

  • Techniques for gathering complete, accurate and objective incident data
  • How to establish root causes
  • Reporting writing

Root Cause Analysis

According to OSHA, a root cause analysis allows an employer to discover the underlying or systemic, rather than the generalized or immediate, causes of an incident. Correcting only an immediate cause may eliminate a symptom of a problem, but not the problem itself.

incident investigation team

Ways to identify a root cause include asking the following questions:

  • If a procedure or safety rule wasn’t followed, why wasn’t it followed?
  • Did production or scheduling pressures contribute to the accident, and, if so, why were these pressures permitted to compromise safety?
  • Was safety training lacking or inadequate? If so, why wasn’t the issue identified, or, if it had been identified, why had it not been addressed?

Asking the above questions and focusing on root causes is necessary to understand why an incident happened, to help develop effective corrective actions, and to minimize or eliminate the consequences of similar incidents in the future.

Some tools that may be used to conduct a root cause analysis include:

  • Brainstorming
  • Checklists
  • Timelines
  • Sequence Diagrams

In addition to the root cause analysis the investigator(s) should ask:

  • What happened?
  • How did it happen?
  • Why did it happen?
  • What needs to be corrected?
  • How can it be corrected?

The benefits of a root cause analysis include:

  • Preventing similar events
  • Avoiding unnecessary costs resulting from:
    • business interruption
    • emergency response and clean-up
    • increased regulation, audits, and inspections
  • Preventing expensive OSHA or EPA fines
  • Preventing litigation
  • An overall safer workplace

OSHA’s publication “The Importance of Root Cause Analysis” provides additional information, assistance and examples of root cause analysis.

Four Steps of a Successful Investigation

Below are the steps you should follow when conducting an investigation.

what to do at the scene

1. Preserve/Document the Scene

Preserve the scene to prevent material evidence from being removed or altered. The investigators can use a number of tools or items to help gather information. They include:

  • Camera
  • PPE
  • Video / Audio recorder
  • Flashlight
  • Measuring devices
  • Warning tape and cones
  • Clipboard and writing pad
  • Batteries
  • Pen or pencil
  • Paint or chalk
  • Ruler
  • Compass

Document the incident facts including the date of the investigation and who is investigating. Some valuable information that should be documented includes the injured employee’s name, a description of the injury, the extent of the injury if known, and the date and location of the incident.

Investigators can also document the scene by video recording, photographing, and sketching.

2. Collect Information

Information should be collected through witness interviews and/or videos (if available). Investigators may also find the following information useful:

  • Equipment manuals
  • Company policies and records
  • Maintenance schedules, records, and logs
  • Training records
  • Audit and follow‐up reports
  • Enforcement policies and records
  • Previous corrective action recommendations
  • Written programs
  • SOPs

Interview Tips

Interviews can often provide useful information about an incident. Interviews should be conducted as soon as possible to ensure the incident is fresh in their mind. OSHA recommends completing them as soon as it is safe to do so. The sooner a witness is interviewed, the more accurate and honest his or her statement will be.

incident investigation interview

An incident investigation always involves interviewing and perhaps even re‐interviewing some of the same witnesses or new witnesses as more information becomes available. Questions should be asked in a way so that they determine as much information as possible about the incident.

Your approach and actual questions may differ depending on who you are interviewing. When interviewing an injured worker, it is important to make sure they are comfortable, at ease, and encouraged to speak freely and honestly.

Some additional interview tips include:

  • Conduct the interview in the native language of the person being interview. It may be necessary to use a translator.
  • Ensure that all interviewees understand that the purpose of the investigation and interview is not fault‐finding but to understand exactly what caused the incident.
  • Communicate that the goal of the investigation is to learn how to prevent future incidents by discovering the root causes of what happened.
  • Make sure the interviewee is in a relaxed atmosphere and avoid asking anything that may be perceived as intimidating or in search of someone to blame for what happened.
  • Ensure that employee know that they can have an employee representative (e.g., labor representative), if available or appropriate.
  • Take detailed notes and if possible, record the interview if the interviewee gives you permission.
  • Ask the individuals to explain what happened in their own words.incident investigations
  • Don’t interrupt the interviewee and encourage them to provide as much detail as possible.
  • Ask open ended questions to avoid a “yes” or “no” answer from the interviewee.
  • Ask the interviewee to clarify when you aren’t sure what he or she is saying.
  • Have blank sheets of paper or a sketch pad handy so that the interviewee can make sketches or diagrams to explain the incident.
  • At the end of the interview give a summary of what the interviewee said and ask them to correct any errors or inconsistencies.
  • Ask him or her what they think could have prevented the incident, focusing on the conditions, actions and events leading up to the injury or accident.

3. Determine the Root Causes

Finding the root causes or underlying reasons why the incident occurred in a workplace is of great importance. Root causes often reflect some type of failure or breakdown in communication within the company. They may reveal that employees were not properly trained; a leaky machine was not repaired or a new employee was not provided with adequate PPE.

Ask Why

Finding the root causes means taking a deep dive into what caused the incident. This requires repeatedly asking “why.” If your root cause is “worker wasn’t paying attention” or “employee didn’t follow the rules” then you didn’t dive deep enough.

To avoid these vague conclusions, you should keep asking “why?.” For example, “Why didn’t the employee shut off the machine before clearing the jam?” If the response is “the employee was in a rush,” then you should ask “Why was the employee rushed?”

The more you ask “why?” the more contributing factors you will uncover and the closer you will get to the root causes. If a procedure was not followed ask “why”? Was the employee rushing to meet a deadline, and, if so, why was production allowed to compromise safety? Or was the safety training the worker received inadequate? If so, why had this issue not been previously identified or, if it had been identified, why wasn’t it completed?

Remember, the incident investigation must focus on discovering the root causes. If an investigation is focused on finding who was at fault, it will not successfully discover the root causes, because it does not discover the underlying causes. The goal should be to find where the gaps are in the system.

4. Implement Corrective Actions –Prevent Future Incidentsimplementing corrective actions

The investigation should be considered complete when all corrective actions addressing the root causes of the incident have been implemented. This part of the investigation should be supported and even involve upper management.

Your findings and how they are presented to workers and management will influence how the information is received. Weak or general corrective actions such as “employees must be aware of their surrounding” or “employees should use lockout tagout procedure when required,” are unlikely to improve the safety culture or to prevent future incidents.

Some corrective actions may take time to implement. The company’s seriousness in implementing challenging corrective actions should reduce the risk of future incidents in addition to preventing accidents, it may also improve the company’s overall safety and employee morale and save the company money.

Some general corrective actions that may contribute to an improved safety program and culture include:  

  • Developing a simple, easy to understand and follow, written safety and health management program
  • Ensuring safety policies clearly establish who is responsible.
  • Make sure the purchasing department includes safety considerations
  • Implement or improve a safety inspection process that includes all levels of employees including management

Your Incident Investigation Program

A successful incident investigation should include:

The Initial Investigation

An initial investigation is an opportunity for employers to identify all unsafe conditions, acts, or procedures that need to be addressed so work can safely resume. until a full investigation has been completed. A preliminary investigation along with the initial report should be completed as soon as possible or within 2-3 days of the incident.

Interim Corrective Actions

From the time of the incident until the conclusion of the full investigation, the employer should take all actions reasonably necessary to prevent the incident from happening again. If you are unable to identify the unsafe conditions, acts, or procedures that contributed to the incident, it may be necessary to shut down an area, an operation, or the entire jobsite. It may also be necessary to reassign the worker(s) involved in the accident until the investigation has been completed.

Thorough Investigationdocumenting investigations

A complete and thorough investigation must determine the incident’s root causes. This involves carefully analyzing the facts and circumstances to identify the underlying factors that led to the incident. It will establish what factors created the unsafe conditions, acts, or procedures. The investigation should also reveal if there any health and safety deficiencies in the management system or a particular process.

Ideally, the report should be completed within 30 days of the incident.

Final Corrective Actions

Upon completion of the investigation the employer should prepare a corrective action report that lists the unsafe conditions and or acts that led to the incident, what corrective actions are necessary, and the steps the company will take to implement the corrective actions.

Also included in the report should be the names and titles of each person who is responsible for implementing the corrective action(s) along with the date of completion for each corrective action. A follow-up meeting should be held to confirm the corrections are being made as scheduled.

OSHA Resources

OSHA Incident Investigation Page

The Importance of Root Cause Analysis During Incident Investigation

Incident [Accident] Investigations: A Guide for Employers

Sources: OSHA, NSC

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