The various photos and videos of the final crash sequence show two major explosions and flame bursts followed by two large black mushroom clouds. Almost reminiscent of a napalm drop. On the assumption that this was the cause of the large conflagration it would raise the question as to why drop tanks were used during a public display.
Below is the link to AAIB report 5/2009 re F6 Hunter which shed one of its drop tanks on to the rwy when landing at Exeter.
https://assets.digital.cabinet-offic...KAXF_05-09.pdf