The video that follows was recently secured from NIST (the National Institute of Standards and Technology) through the Freedom of Information Act and reveals as clearly as any evidence will that the Twin Towers were brought down by explosions.
Three firemen describe three explosions, after which WTC1 collapsed. One of the firemen speculates the explosions could be in other buildings, which could also collapse. Well, of course, WTC7 did, from more explosions, later that day.