truck caught fire while block heater was plugged in on 1994 Ford F-350

how do I find out if fire was caused by recalled part and what steps can I take to get it fixed by them if there is anything that can be done. It was bought from a private party and we've been told that it could've been the speed control switch. Can anyone please point me in the right direction?

Asked by for the 1994 Ford F-350