wow, sux! I hope you chucked it in the trash...or the recycle center. don't use it anymore! I had a small fire in my upstairs a few years ago...luckily, I have fire insurance, and 3 fire extinguishers around my house and wasn't growing then. fire dept did show up, but they didn't really have anything to do, I had already put it out myself...scary thing that. glad they did though, needed the fire report. insurance co. paid me $5000, as a renter and the owner of my house $3000, that I know of. in your case, if you don't have insurance, you'd probably just go to jail. certainly, if the fire dept show up, they'd report you for growing.
get insurance, if you ain't got it...growing is a fire hazarrd, even if we're careful. at the least, buy a min of 2 extinguishers, of any size. keep one in the grow area and one farther away.
P.S. did you figure out what the cause was? condensation comes to mind...faulty wiring...corrosion, caused by moisture...a short, caused by some loose/free piece of metal inside...