Which classification of cause includes incidents that are not easily explained?

The classification of cause that includes incidents that are not easily explained is "Undetermined." This category is used in fire investigations when the evidence does not support a clear conclusion about the cause of the fire. Events that are classified as undetermined typically occur when there is insufficient evidence left at the scene, or when the damage is so extensive that determining the origin and cause becomes challenging.

In practice, this classification acknowledges the complexities involved in fire investigations. There are times when a fire's cause cannot be conclusively identified due to various factors, such as lack of witnesses, destruction of evidence, or even variable combustion scenarios that make it difficult to discern how or why the fire occurred. Thus, classifying an incident as undetermined allows for reflection of the uncertainty that investigators may face in their assessments.

In contrast, the other classifications—accidental, natural, and incendiary—are more definitive in nature. Accidental incidents can be explained through a clear cause, such as malfunctioning equipment or human error. Natural causes relate to events like lightning strikes, where the origins are inherently identifiable. Incendiary causes involve intentional actions, clearly indicating a human factor that instigates the fire. Therefore, in investigations where clarity is lacking, undetermined is the appropriate classification