How did the fire start at the 2012 Daytona 500 race?

During the 2012 Daytona 500, something in Juan Pablo Montoya's car broke while he was driving around the track under caution, sending his car up the race track and into the rear of one of the jet dryers which was cleaning up the debris. Jet fuel poured down the banking of the track and a spark set the fuel on fire.