It left a gaping hole in the wall above the Path underground station. Most of those who died are believed to have been crushed by the station ceiling.

It ripped through three floors of concrete, scattering ash and debris and set off a fire that sent choking smoke and flames up through one of the 110-story "Twin Towers".

Total pandemonium

Thousands of office workers were trapped as smoke billowed up through the buildings.

With no working lifts or lighting there was total pandemonium.

People did not know whether to stay in their offices or brave the journey down via the smoke-filled stairwells.

"It felt like an airplane hit the building," said Bruce Pomper, a 34-year-old broker.

Desperate for air, some people smashed windows with office furniture.

Hundreds eventually poured out of the building gasping for air and covered in soot.

Rescue workers struggled to get oxygen to those in the upper floors. About 100,000 people work in and visit the 1,700ft towers every day - the blast happened at their busiest time.

Several people have called New York's police claiming they were behind the attack but authorities are keeping an open mind about possible suspects.

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