The source of the molten material was aluminum alloys from the aircraft, since these are known to melt between 475 degrees Celsius and 640 degrees Celsius (depending on the particular alloy), well below the expected temperatures (about 1,000 degrees Celsius) in the vicinity of the fires.
Pure liquid aluminum would be expected to appear silvery. However, the molten metal was darker as it would have very likely mixed with large amounts of hot, partially burned, solid organic materials (e.g., furniture, carpets, partitions and computers) which can display an orange glow, much like logs burning in a fireplace.
Its more fun to follow a conspirancy theories than the boring /simpler (bad) news.
It was just terrorists and not the USA government.
