An article published by The Open Chemical Physics Journal in 2009 details that a team of scientists lead by a Danish University of Copenhagen researcher have found traces of what appears to be unreacted and partially reacted super-thermite, or nano-thermite, in four different samples of the World Trade Center dust collected by eyewitnesses. The unique compound shows immense reactivity to heat and ejects the same iron-rich spheroids observed in the ignition of commercial thermite.

An English-subtitled Danish television interview with the lead researcher, Niels Harrit, who believes that the discovery of this thermite compound implies foul play, is shown below, followed by an abstract from the research paper.