The hoist elevator fell more than 20 floors

NEW YORK (CNN) -- A construction elevator plummeted from the side of a skyscraper in New York's Times Square area Tuesday, injuring at least 11 people, creating traffic chaos and forcing evacuations, officials said.

The injuries occurred when a hoist elevator along with part of a scaffolding and a crane collapsed on the 23rd floor and fell onto the roof of a neighboring hotel during the morning rush-hour.

City officials said it was not yet known what caused the accident at the 4 Times Square site, where the Conde Nast publishing company is establishing new offices.

"We are evacuating three buildings in the area, including a hotel," said New York City Fire Department spokesman Frank McCarton.

Officials said more than 250 people were being evacuated. More than 100 firefighters and 25 units were called to the scene.

Gridlock paralyzed the heart of Manhattan as the area was cleared for emergency crews to gain access to the site. Several blocks were closed to traffic and pedestrians for several hours after the accident at 8:30 a.m. EDT.

The Conde Nast building is due for construction completion next year.