Debris was blown by the force of the compressed air over several blocks. You saw the clouds of debris rolling down the street.
There were no bombs no matter how much the paranoid wackos want to believe.
See this link to read an INFORMED AND PROFESSIONAL opinion on how the buildings came down. Architectural Record on WTC
The explosions and raging fires severely weakened the remaining columns, which were already overloaded by the breaches caused by the crashes. Jet fuel releases much more heat than paper and plastic, which typically fuel office fires, said David A. Lucht, director of Worcester Polytechnic Institutes Center for Fire Safety Studies. Fireproofed steel loses half its strength when it reaches 1,100°F and fails rapidly above 1,600°F; temperatures inside the building were likely even higher.