Fire usually connotes presence of fuel....what else in a small helicopter is there that would produce a serious fire?
Ask the simple questions first before making your own determination of what caused the crash please.
Are all the rotating bits present at where the wreckage is located?
Do the Rotor Blades, main and tail, show rotational damage?
How large is the debris field...small/compact or wide/scattered?
Weather conditions?
Radio Transmissions reporting any problems or malfunctions?
Don't go running off with LTE or VRS without any evidence....that is so amateurish.