The act, condition or situation that allowed the heat source to combine with the material first ignited to start a fire. It also includes fires that were deliberately set, but there was no criminal act involved because the person burned his or her own property with no intent to defraud. Suspicious fires are those where evidence supports the possibility that the fire might have been deliberately set, but the evidence is not strong enough to conclude incendiary.
Further investigation is necessary.
A fire started because of an electrical or manual control failure, failure to maintain or replace parts or equipment all fall under this category.