Here's my take Steve,
The fire is accidental. It was not the intention of the burglary to burn the house. But, many state laws hold that accidental fires started during the commission of a felony are "Arson." In Illinois, when I was a Bomb and Arson investigator (many years ago), the mere possession of a Molatov Cocktail, was Arson, even if no actual fire occured at all, even to the wick. An unitenional fire cannot be incendiary, but can be a crime.
Pat Kennedy, CFEI, CFPS, MIFireE
Fire and Explosion Analyst
Sarasota, Florida
[
www.kennedy-fire.com]