Dust rises as the remains of the tower are toppled

Firefighters and people working at Ground Zero, watched as the 15 metre-high steel section came down in a cloud of dust.

Workers had spent most of the morning cutting away at the base of the building facade with blowtorches, before it was pulled down by a truck.

Officials said the fragment - part of the 110-storey north tower - would be saved for a possible future memorial.

A section of the south tower, removed several weeks ago, has also been saved.

Ceremonies

Both towers collapsed on 11 September, when two passenger planes were piloted into the buildings by suicide hijackers.

A third jet slammed into the Pentagon in Washington DC and a fourth hijacked plane came down in Pennsylvania.

More than 3,000 people died in the attacks - many of them will never be identified.

Last Wednesday, ceremonies were held across the world to commemorate those who lost their lives in the attacks three months ago.