::Here are some references for "molten metal" found in the remains of the buildings: 
 ::* "In some pockets now being uncovered, they are finding molten steel." Alison Geyh, PhD. Johns Hopkins Public Health Magazine (ref) 
 ::* "Feeling the heat, seeing the molten steel, the layers upon layers of ash, like lava, it reminded me of Mt. St. Helens and the thousands who fled that disaster". Ron Burger, public health advisor. National Environmental Health Association (ref) 
 ::* "They showed us many fascinating slides" he continued, "ranging from molten metal which was still red hot weeks after the event, to 4-inch thick steel plates sheared and bent in the disaster". Dr Keith Eaton. Journal of the Institution of Structural Engineers (ref)(pdf, page 6) 
 ::* "As of 21 days after the attack, the fires were still burning and molten steel was still running." Structural Engineers Association of Utah (ref, page 3) 
 ::* "Sarah Atlas and her canine partner, Anna, a black-faced German shepherd, were deployed by New Jersey’s Task Force One Urban Search and Rescue. [...] Fires burned and molten steel flowed in the pile of ruins still settling beneath her feet." University of Pennsylvania (ref) 
 ::* "Thermal Imagery of the progression of molten steel hotspots from September 18 to September 25." City University of New York (ref)(pdf, page 5) 
 ::* "Underground, it was still so hot that molten metal dripped down the sides of the wall from Building 6." 9-11 Commission, Public Hearing (ref)