Professor Steven E. Jones was able to get ahold of a sample of a material found on the exterior of one of the steel beams of the WTC that was being held in a memorial of 9/11 (the only steel that wasn't immediately scrapped before it could be examined was sent to multiple memorial parks). He claims that within that sample are found the by-products of thermate, a compound of thermite and sulpher which is specifically used in demolitions to cut through steel support beams.
Steven E. Jones has taught graduate courses on Archaeometry, which is a branch of physics used in forensics to reconstruct crime scenes, so he's certainly an expert on the subject. He personally told me that he has documented the chain of custody of this evidence on thermate in the WTC and is in the process of publishing it. He intends to submit this evidence for further independent experimentation in order to confirm it's authenticity.
It's very curious that the steel beams where sent to scrap yards before they could be examined, espeically considering all the eyewitness testimony claiming that bombs had gone off and other corraborating evidence concerning the use of demolitions. The most accurate way to understand if explosives where used would be to examine the steel, and thus it's very odd that investegators where prevented from examining this steel, especially in light of Professor Jones' work.
Edited, Jul 9th 2006 at 6:43pm EDT by Dronadesh