I have seen posts like this before, AirBnB is a booking service, contact them, well why, what do you expect somebody in a call center to do?
As far as is know there was not even a guest present when this happened.
Likewise might be interesting to find out when the guest left, but not sure what is otherwise expected, them to say they had caused a fire and left asap?
No mention of Insurer, which would be the next call after the fire brigade, so I assume there is not any Insurance.
Assuming you are remote I would want to go look see what happened and talk to the Fire Dept. Sometime they can tell or at least indicate how it happened. I am also under extreme fire danger, it is a tinder box out there, no rain for a very long time, sould have snow on the ground. We have not had any incidents locally, well not yet.
David