Thousands of New York firefighters stormed Ground Zero and clashed with police.
They were protesting against the scaling down of rescue work on the site.
Several firefighters were arrested as they protested against the move to cut numbers working on the operation to just 24.
At the height of rescue efforts, up to 2,500 firefighters were deployed at Ground Zero.
Demonstrators seized cranes used by construction workers and turned them into podiums as they spoke out against the move, which has also seen the number of police working on the site slashed to 24.
Later, they marched on City Hall in an attempt to take the message direct to Mayor Rudolph Giuliani, but were blocked by a wall of police, some wearing riot gear.
Kevin Gallagher, president of the United Firefighters Association, told the crowd that numbers must be increased to allow the bodies of their colleagues to be rescued.
Brooklyn Trustee for the Uniformed Firefighters Association Matty James has called the move to slash numbers "disgusting", saying this week alone the bodies of 12 firefighters were pulled from the wreckage.
"The city may be ready to turn this into a construction job, but we're not. We want to our brothers back," he said.
Officials say the site is unsafe and risky recovery operations under unstable rubble could lead to more deaths. They are trying to introduce a more tightly controlled operation.
PA