Again, there were other things that burned, the Jet Fuel only started the Fire, also, watch the Videos, if you look at the way the building fell, it couldn't have been from explosives.
The fire was only what finally broke(using that metaphorically) the Structure, after there was a Hole in it, the building came down because the Floors could not hold 1000X what they should have held, after the Structure around where the Plane hit finally gave