New theory on Twin Towers' collapse

Explosions triggered by molten aircraft metal reacting with water from sprinkler systems may have felled the Twin Towers after the 9/11 attacks, according to a new theory.

Just before the two World Trade Centre skyscrapers in New York collapsed on September 11 2001, powerful blasts were heard within the buildings and a leading materials scientist says they could be the key to the dramatic conclusion of the terrorist attacks.

Over-heated steel beams have been blamed for the towers suddenly crashing to the ground after they were hit by two passenger jets.

But Norwegian expert Dr Christian Simensen believes the powerful explosions were caused by a chemical reaction between molten aluminium from the aircraft and water ripped out the buildings' internal structure.

"Both scientific experiments and 250 reported disasters suffered by the aluminium industry have shown that the combination of molten aluminium and water releases enormous explosions," said Dr Simensen, from the SINTEF institute based in Trondheim, Norway.

Almost 3,000 people died after al Qaida terrorists flew two fuel-laden passenger jets into the World Trade Centre in Manhattan. The impacts triggered massive explosions and fires, but the subsequent collapse of each tower came as a shock and surprise to those watching the disaster unfold.

Explosions heard just before the buildings fell have led to claims that explosives were set off inside the towers.

Dr Simensen believes after crashing into the skyscrapers the two jets would have been trapped within an insulating layer of debris. As a result, the aircraft hulls rather than the buildings absorbed most of the heat from the burning aviation fuel.

Molten aluminium from the jets, flowing down through staircases and gaps in the floors, reacted with water from emergency sprinklers on the lower levels, it is claimed.