Nails In The Coffin of Trade Seven - WTC-7 Collapse Footage Shows Unmistakable Demolition Charges November 27, 2004
Squibs along southwest corner of WTC-7 (mpeg)
QuickTime version of above
The above clip is taken from this longer video of the WTC-7 collapse, which itself is a small segment of the Naudet brothers' documentary "9/11" , (with enlargement and cropping by Webfairy):
Full sequence from the 9-11 DVD
Looking at the upper right-hand corner of the building we see a rapid series of small explosions travelling upward just as the building itself begins to fall. The size, placement and timing of these "puffs" is very consistent with squibs from cutting charges of the type used in professional controlled demolitions, and in fact nothing but small explosive charges could create such an appearance. The decreasing volume of the building from the collapse itself could not create enough pressure to cause such localized high-velocity effects, and this early in the collapse would have only created a modest overpressure.
Other video evidence of squibs:
Larger mid-wall squibs in the WTC-1 collapse
Slow-motion view showing several well defined, roughly spherical squibs Quicktime
More distant view of WTC-1 from the north
Two very sharp and elongated squibs can be seen on the right side of the building mpg
(The above are from the Collapse Update page)
Other evidence for explosive cutting charges
More on the WTC-7 collapse