NEW YORK (CNN) -- Three 60-foot steel beams fell 40 stories at the World Trade Center construction site Thursday after a crane cable snapped.
Authorities said no one was injured when the beams -- each weighing several tons -- came hurtling down from one of the new towers being built at the site of the September 11, 2001, terrorist attacks.
"The cable of a crane broke, causing the steel it was lifting to fall approximately 40 stories back onto the flatbed truck that had transported the steel into the World Trade Center site," said a statement from John Gallagher, spokesman for Tishman Construction, which manages the site. "The incident occurred within an enclosed section of the site, which is not accessible to the public."
The 72-story building, which will face the World Trade Center memorial park honoring the victims of 9/11, is scheduled to officially open in the fall of 2013, according to the World Trade Center website.
"Fortunately... nobody was hurt," New York Mayor Michael Bloomberg said at a news conference Thursday.
Gallagher said in his statement that the construction company was "investigating the matter in full cooperation" with authorities including the New York fire department, the Port Authority of New York and New Jersey and the city's Department of Buildings.
"The job is partially shut down pending the investigation," Gallagher said.