Which of the following is a possible indicator of incendiary fires?

The presence of accelerants is a significant indicator of incendiary fires. Accelerants are substances that can enhance the speed of combustion, making a fire burn more intensely and spread more rapidly than it would under normal conditions. Identifying these substances at the scene of a fire suggests that it may have been deliberately set, as an arsonist would use them to achieve specific targets or create specific effects during the act of setting a fire.

In the context of fire investigation, techniques are employed to look for residues of accelerants such as gasoline or other flammable liquids. Their identification can strongly support the hypothesis that the fire was intentionally ignited rather than occurring due to accidental causes or natural events. This helps investigators in determining the intent behind the fire and can be crucial for legal proceedings.

Other options like a single point of origin may suggest suspicious circumstances, but they can also occur in accidental fires. Evidence of natural causes and the fast extinguishment of the fire tend to align more with non-incendiary scenarios, making them less indicative of arson. Thus, the presence of accelerants stands out as the most definitive indicator of incendiary activity in fire investigations.