1) Many people witnessed the fireball, and described falling elevators, in the basement.
2) People, like Felipe David on B2 and Jose Sanchez on B4, suffered flash burns.
3) People, including William Rodriguez on B1 and Mike Pecoraro on B6, smelled kerosene after the blast. Do you think that's a coincidence?
4) All the explosions were reported at or near the freight elevator. People described a fast, hot wind.
5) There is no evidence of structural damage in the basement, much less damage from explosives massive enough to damage core columns. (Think of the photo I posted of the 1993 bomb damage, which did not destroy the parking garage columns.) The core walls were made of gypsum wallboard.
6) No one describes anything like a high explosive. No one was blown to pieces. High explosives do not produce persistent fireballs. The people in Turner's field office thought a bomb had gone off: a natural assumption. However, there isn't a single shred of evidence of a bomb going off, nor is it logical that a small bomb would be there. All evidence, from the impact zones down, is consistent with jet fuel igniting in the elevator shafts.
7) This happened in both towers.