HUNDREDS OF engineers have volunteered to help the rescue and recovery effort, being led by the New York City Department of Design & Construction.
And major contractors have started to pick apart the wreckage of the World Trade Center's twin towers.
Structural and civil engineers are working in the rubble, and in teams carrying out structural surveys of buildings near the disaster zone.
Co-ordination of the volunteer effort has been led by the Structural Engineers Association of New York (SEAoNY).
Member firms include British consultants Arup, Buro Happold, WSP subsidiary Cantor Seinuk and Dewhurst MacFarlane.
New York consultant Thornton-Tomasetti is leading structural survey work and co- ordinating the volunteer engineering effort.
The re-opening of Wall Street for Monday was given priority by the City. Within the police cordon around Ground Zero, teams of structural engineers engaged privately by financial services firms checked buildings visually to see if more detailed checks were needed.
Deep inside the police and army cordon teams of four engineers, generally from the same firm, are working on an initial assessment of structures in the blocks surrounding the disaster site.
'The work has been divided into sections, with each team dealing with four blocks, ' said Arup senior associate Nancy Hamilton.
Inside the disaster area, other teams of engineers - also of four -are directing the safe removal of rubble and pieces of the structure.
Teams are working 12-hour shifts, directing police, FBI and firefighters safely through the carnage.
Debris is being removed by barges to a landfill site in Staten Island, where it is then to be further sifted through by FBI investigators. By Saturday, only 1% of the 1Mt of debris had been shifted.
Contractors Amec and Bovis LendLease are responsible for the 'surgical demolition' of the wreckage that was the World Trade Center's south tower.
The firms are co-ordinating subcontractors involved in picking apart collapse debris. A Bovis LendLease spokesman said on Tuesday that the team was still holding out hope of finding survivors a week after both towers crashed to the ground.
The firms have also been involved in emergency repairs to damaged electricity, telecommunications, water and gas infrastructure.
The exclusion zone, has been divided into four quadrants.
Amec/Bovis Lendlease have two, which include the south tower, extending south and west. New York-based contractors Turner and Tishman have responsibility for a quadrant each.