Source of info above from American Free Press. Or just call Popular mechanics and ask for yourself.
I still maintain the concerns associated with building number 7 and am repulsed by the whitewashing propaganda by Chertoff that provides no real explaination of what happened - and unfairly labels free thinking people like myself and others an "extremist" or "conspiracy theorist." Chertoff, of course being the cousin of the Secretary of the Department of Homeland Security.
http://911research.wtc7.net/essays/pm/ - this is a good essay explaining Chertoff's propaganda, although I don't agree with all of it.