Undetermined Fire Cause is used when the specific cause has not been determined to a reasonable degree of probability.

• A. Fire cause determined to a reasonable degree of probability.
• B. Fire cause classification used when the exact cause has been determined to a high degree.
• C. Fire cause classified as due to natural causes.
• D. Fire cause classification used when the specific cause has not been determined to a reasonable degree of probability.

Answer: (D)

Undetermined fire cause is used when the specific cause has not been determined to a reasonable degree of probability. In practice, investigators look for evidence that points to a single, probable origin and cause. If the evidence is inconclusive, the scene is too deteriorated, or several potential causes could explain the fire without one standing above the others, the determination remains undetermined. This category signals that no specific cause meets the required level of probability, and it allows for re-evaluation if new information becomes available.

If a cause can be identified with a high degree of probability (such as a clearly identifiable accidental or natural cause, or a confirmed intentional act), that would be documented instead. The undetermined label is the appropriate choice precisely because the evidence doesn’t support a specific, probable cause.