Our dryer fire started in the motor, lint had built up behind the wires. If you look at your dryer manual, it says the dryer should be taken apart every two years by a certified electrician and cleaned, not just the bottom of the dryer and the vent hoses. Our dryer vent was totally clean. After researching Frigidaire dryer fires, it's seems to be a very common occurrance, even with models less than a year old. Needless to say, we didn't replace our appliances with the same brand.
I have a whole new perspective on fires, I won't even burn a candle now!