Celica Forums General Discussion General Fire under the hood

I took my 2000 celica gts to have a new clutch installed, the mechanic put in clutch flywheel and passenger side axle cv joint. I picked up the car drove it home less than 40 minutes later, turned it off. went inside and an additional forty minutes later the car was on fire under the hood on the driver side. the fire rapidly spread and the car was totaled in 10 mins or less. What could the removal of the transmission and the changing of the clutch bring about a fire under the hood