Jimmy,
The proper wording for the classification of the cause as described above would be "undetermined."
Remember that in 921 there is a big difference between the "fire cause" and the “classification of the fire cause”. “3.3.55 Fire Cause. The circumstances, conditions, or agencies that bring together a fuel, ignition source, and oxidizer (such as air or oxygen) resulting in a fire or a combustion explosion.” The cause of the fire would be the pan of oil being left on the stove with the eye (burner) on.
“19.2.1 Classification of the Cause. Classification of a fire cause may be used for assignment of responsibility (see Section 18.6), reporting purposes, or compilation of statistics.”
The classification of the cause, whether negligence or intentional, could be accidental or incendiary.
I hope this helps. It is not as confusing as some people make it. Just keep the differences in definitions between “cause” and “classification of cause” in mind.
Pat Kennedy, CFEI, CFPS, MIFireE
Fire and Explosion Analyst
Sarasota, Florida
[
www.kennedy-fire.com]