[Calpernia]

There were explosions. Here is coverage of the 911 calls.

http://cf.wnbc.com/ny/sh/videoplayer/video.cfm?id=1317794&owner=ny

Forte Runningrock at post 111 seems to have a good explanation about that though.

[Sender]

"Why would terrorists undertake straight-down collapses of WTC-7 and the Towers when 'toppling over' falls would require much less work and would do much more damage in downtown Manhattan?" Jones asks. "And where would they obtain the necessary skills and access to the buildings for a symmetrical implosion anyway? The 'symmetry data' emphasized here, along with other data, provide strong evidence for an 'inside' job."

Why, indeed, would terrorists perfectly drop buildings into a pile when it's much easier (and more plausible) to knock out one corner and hope they would fall across several blocks, doing ten times the damage?

Either you have a tinfoil conspiracy theory, or you accept the obvious...the buildings just fell down due to gravity.

[concretebob]

If you are not familiar with the interior mechanical elements..i.e., HVAC, water lines, gas lines, hydronic piping, (heating water), of a commercial building, you can't know what will happen during an intense fire.
Lines already pressurized, will explode when heated.
Methane gas from sanitary waste-lines will explode.