Early report from Reddit - not a lot of detail but the dangers of gasoline and hot metal are always there, especially if you are acting carelessly. In the second photo it seems that the fuel hose is not attached to the filler and the clamp is missing, but it isn't clear if anyone has been working on the car post-fire.
Bummer for the owner.Customer trailered in this beauty
Apparently caught fire during the refueling process at a race.
Needless to say, it might need a few new parts.
Large blob of melted plastic is the intake, lefthand side is the fuel throat, cables and whatnot is the wiring assembly.
The cause has yet to be determined.