As to the original FEMA investigation of WTC 7 they concluded, "The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence. Further research, investigation, and analyses are needed to resolve this issue."
Yes, I know that aftewards, NIST continued to 'resolve' these issues. Here's an excerpt of their 5 year effort in action:
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Molten metal? What molten metal?
NIST, in its final report on WTC 7, ignored all of the evidence relating to molten metal, even though numerous reliable witnesses spoke of the presence of molten metal at Ground Zero. These witnesses included Richard Garlock, a structural engineer at Leslie E. Robertson Associates, an engineering firm involved in the design of the towers and the clean up of the site, who said "Here WTC 6 is over my head. The debris past the columns was red-hot, molten, running."10
The witnesses to molten metal also included University of California, Berkeley engineering professor Abolhassan Astaneh-Asl, who was the first scientist given access to the steel at ground zero. Dr. Astaneh-Asl referred to the WTC steel he found as "kind of melted."11 Years later, when asked again about his experience he clarified, "I saw melting of girders in World Trade Center."12
There are many other reports of molten metal at ground zero, including quite a few from those who support the Bush Administration's ever-changing fire-induced collapse theories. There are also photos supporting the reports of molten metal.13 But NIST continues to ignore all of this evidence in its new report.
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http://www.911truth.org/article.php?story=20080911073516447
It goes on, making it clear that NIST ignored a lot of evidence, including paper thin steel and sulfidation, the possibility of nano-thermite being used (it would handily account for the 'mysterious' sulfidation and extreme thinning of steel) and having ignored all this evidence, concludes "The reason for the collapse of World Trade Center 7 is no longer a mystery".