Also, I know one was from an illegal grow.
Here.
Involved some gasoline. Not all details are in yet.
One year, right after a fire evac got lifted, we almost had another one start next door.
Illegal grow had jumped the meter at the box, pulled too many amps, seevice wire insulation caught fire, was melting, trying to start a grass fire. Rob and I called that one in and kept it contained till PG&E and our Sherriff's got there.