This clear video has a sound track with three bangs on it. The delay
between explosions and bangs do not appear right, though there could
be a microphone open near the site. It could just be a fake sound
track. However, it appears the two buildings to the left (#2 and
#1?) could have been hit by debris, and there might have been an air
burst of some kind too, near the top of the big plume. Notice the
tower to the left disappearing momentarily in nearly invisible dark
smoke.
http://www.youtube.com/watch?v=UPbmPyMxu0Y
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/