About 1:40 from start this smoke sequence can be seen:
Smoke view 1
A lot of white smoke along the right side and at the base of the tower(2) and its barely visible.
Unfortunately the video is broken up in 2 sequences, so it's not easy to decide the gap between the to clips shown here. The clip below starts about 2:35 from start.
Smoke view 2
Most of the smoke has cleared out. You can actually se WTC-3 in the back.
It's reasonable to think that the white smoke is from one (or more) of the many explosions reported in, below and around the towers. But some of the smoke clearly come from the right side of WTC-2. A line of smoke puffs i visible from somewhere above impact to bottom.
The clip below is from Smoke view 1; enlarged and in slow.
Enlarged and slow from "Smoke view 1"
Below another sequence with the puffs of smoke from the same video.
Vertical line of smoke
And another frame from the same video showing the clear signs from explosives.
Here some other videos showing the distinct explosion-smoke-pattern on the facade.
One on each floor - to the right. Here some witnesses (from 9-11 Research):
Kennith Rogers -- Firefighter (F.D.N.Y.):
Meanwhile we were standing there with about five companies and we were just waiting for our assignment and then there was an explosion in the south tower, which, according to this map, this exposure just blew out the flames. A lot of guys left at that point. I kept watching. Floor after floor after floor. One floor under another after another and when it hit about the fifth floor, I figured it was a bomb, because it looked like a synchronized deliberate kind of thing. I was there in '93.
Karin Deshore -- Captain (E.M.S.):
Somewhere around the middle of the World Trade Center, there was this orange and red flash coming out. Initially it was just one flash. Then this flash just kept popping all the way around the building and that building had started to explode. The popping sound, and with each popping sound it was initially an orange and then a red flash came out of the building and then it would just go all around the building on both sides as far as I could see. These popping sounds and the explosions were getting bigger, going both up and down and then all around the building.
A little bit higher up the tower, you can see smoke coming out. There was a lot of these smoking holes in top of both towers, some with fires and some just smoking.
This one here (like many others) are so far away from the impact zone, that it must have been caused by a bomb.
The string of puffs seems to start at this very isolated smoking hole and continues down - maybe to ground level. In the video in question we can see how such a smoking hole (probably) was started. This explosion look strange and doesn't seems to be caused by the fire.
In this low quality clip there even seems to be a clear flash moving from the smoking hole and down. It could be a very big piece of paper falling straight down ... : )
