Guide · Occupational safety and health
Cause tree analysis accident investigation step by step
The cause tree starts from the injury and works backwards, fact by fact, to the causes nobody saw. Here is the method from Chile's Public Health Institute (ISP), a plant example you build click by click, and what Chilean regulations require after an accident: DIAT report, investigation and records.
Informational guide, not legal advice. Check the current regulation at Ley Chile (Chile's official law library) and consult your safety professional or your mutual insurer (mutualidad).
Start from the last fact: the injury. It is the only one known for certain.
The method
How to build a cause tree
Chain
Conjunction
Disjunction
Independent
The ISP guide does it in three stages: gather the information, build the tree and manage what comes out of it.
- 1. A third-person narrative, step by step, with no assumptions or judgments.
- 2. The list of facts, numbered in chronological order.
- 3. From the injury: what was needed? Was another fact required? Until there is no answer.
- 4. Each root cause with its corrective and preventive control.
The example
From the tree to controls: one per root cause
A made-up example of a slicer in a food plant. The controls target the causes at the far left, not the injury.
Order behind: the line is not stopped
Control
Slicer cleaning is scheduled with the line stopped and does not depend on how far behind the day is.
No cleaning tool at the station
Control
A cleaning tool fixed at the station, included in the daily inspection.
Maintenance with no close-out checklist
Control
A close-out checklist that verifies the guards before the machine is released, signed by whoever receives it.
| Root cause | Control |
|---|---|
| Order behind: the line is not stopped | Slicer cleaning is scheduled with the line stopped and does not depend on how far behind the day is. |
| No cleaning tool at the station | A cleaning tool fixed at the station, included in the daily inspection. |
| Maintenance with no close-out checklist | A close-out checklist that verifies the guards before the machine is released, signed by whoever receives it. |
After the accident
DIAT report, investigation and records: what the rules require
Medical care
Requirement
The injured person is sent immediately to the insurer's medical center (the employer's mutual or the ISL).
Source
DIAT
Requirement
The employer files the DIAT (Individual Work Accident Report) within 24 hours of learning of the accident.
Source
Investigation
Requirement
The employer investigates the causes, directly or with the joint health and safety committee, using the methodology set by its insurer.
Source
Serious and fatal
Requirement
The insurer investigates, and the investigation follows the cause tree methodology.
Source
Records
Requirement
Place, date and time, people, description, causes and corrective actions for each incident, plus a record of each accident.
Source
| Step | Requirement | Source |
|---|---|---|
| Medical care | The injured person is sent immediately to the insurer's medical center (the employer's mutual or the ISL). | DS 101, art. 71 a) |
| DIAT | The employer files the DIAT (Individual Work Accident Report) within 24 hours of learning of the accident. | DS 101, art. 71 b) |
| Investigation | The employer investigates the causes, directly or with the joint health and safety committee, using the methodology set by its insurer. | DS 44, arts. 47 and 71 |
| Serious and fatal | The insurer investigates, and the investigation follows the cause tree methodology. | SUSESO Compendium |
| Records | Place, date and time, people, description, causes and corrective actions for each incident, plus a record of each accident. | DS 44, art. 73 |
In the app
How the app tracks incidents and their controls
The incident is logged on the spot, controls get an owner and a deadline, and the period comes out as a signed PDF.
Get early accessFree app, in early access.
Frequently asked questions
Cause tree analysis FAQ
What is the cause tree method?
An accident investigation method that starts from the last fact, the injury, and works backwards asking what was needed for it to happen. The result is a diagram of the facts and how they relate, which brings out causes that are not obvious at first sight.
Is the cause tree method mandatory?
In Chile, for serious and fatal accidents, the insurer's investigation must follow the cause tree methodology, according to the Compendium of SUSESO (Chile's social security regulator). For all others, DS 44, Chile's Supreme Decree 44, requires the methodology set by your insurer (art. 71).
What is the DIAT and what is its deadline?
The Denuncia Individual de Accidente del Trabajo, the individual work accident report. The employer files it with its insurer within 24 hours of learning of the accident (art. 71 of DS 101). If it does not, the injured worker, the joint committee, the treating physician or anyone who knows the facts can file it.
What is the difference between a conjunction and a disjunction?
In a conjunction, a fact needs two or more independent antecedents to occur. In a disjunction, a single fact causes two or more facts. In a chain, a fact has a single cause.
Who investigates an accident at the company?
The employer, directly or through the joint health and safety committee and the prevention department where applicable (art. 71 of DS 44). Investigating causes is one of the joint committee duties (art. 47).
What goes in the accident narrative?
What happened, in the third person and step by step: who, what, when, where, how and the consequences. The guide from the ISP (Chile's Public Health Institute) asks for no assumptions, interpretations or value judgments.
Does the iGromi app log incidents?
Yes. The incident is logged from a phone with photo, name, time and place, signed, and included in the PDF for the period with a verification code. The app is free and in early access.
Sources: DS 44 (BCN) · DS 101, art. 71 (SUSESO) · SUSESO Compendium, DIAT · SUSESO Compendium, serious and fatal accidents · ISP, accident investigation guide. Reviewed on November 1, 2026.
Keep reading
Occupational health and safety guides
DS 44: the records it requiresThe hub: every preventive-management record, with its article.DS 594 summarizedWorkplace sanitary and environmental conditions, title by title, with their limits.Joint safety committeeDuties, election, job protection and the safety delegate.Risk matrixHow a risk is assessed, with worked plant examples.5-minute safety talksReady-made topics by hazard, plus the attendance record.IRL under DS 44What the occupational risk information must say and when it is delivered.Risk mapWhat the DS 44 risk map includes, with a plant example.Internal safety regulationsWhat the health and safety regulations contain and how they are published.PPE issue logWhat to record when personal protective equipment is handed out.Accident rate calculatorAccident, lost-day, frequency and severity rates with their formulas.TMERT protocolChecklist, risk levels and deadlines of the MINSAL musculoskeletal protocol.Safe work procedureWhat an SWP is, its sections and a food-plant example.
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