NEW YORK (AP) _ The company that constructed the 14-story scaffold that collapsed at a Manhattan office building, killing five construction workers, was fired after officials learned of the firm's troubled past.

Ten other workers, a pregnant bystander and 15 firefighters and police officers also suffered injuries after the scaffold collapsed. City officials said Thursday the scaffolding was constructed without a required permit.

Police said a heavy concrete load placed on the structure may have caused part of the scaffold to sway and buckle, eventually leading to the collapse.

Authorities responding to the accident had to call in rescue teams from the World Trade Center, two miles away.

Buildings Department spokeswoman Ilyse Fink said the department has yet to find a cause and is still investigating the collapse. She said Nesa Roofing and Restoration, which hired Tri-State Scaffolding and Roofing to construct the scaffold, hadn't obtained the required permit.

The leasing agent for the office building, Stephen Green, fired Nesa on Thursday after reporters called asking about the firm's troubled history, said Gerald McKelvey, a spokesman for Green.

Constantine Stamoulis, one of Nesa's owners, was arrested in May for allegedly hiring someone to impersonate him at a city examination required to obtain a Special Riggers license. The license allows the holder to hoist or lower up to 1,200 pounds of material by rigging set up on a building's exterior.

Stamoulis pleaded guilty to disorderly conduct in June and paid a $250 fine and served 10 days of community service, said Barbara Thompson, a spokeswoman for the Manhattan district attorney's office.

None of the owners of the company, including Stamoulis, returned telephone calls for comment. A message left at Tri-State's office in Deer Park, N.Y., also was not returned.

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Editors: Associated Press Writer Donna De La Cruz contributed to this report.