Smoke could be seen coming from the Midtown building.
The building was not evacuated.
A firefighter suffered a minor injury when debris fell on him. An engineer also suffered some minor smoke inhalation, but refused medical attention.
As of 8:30 a.m. Monday, there was still a heavy presence of emergency vehicles closing off the street in front of the building on Fifth Avenue.
There is no word yet on the cause of the fire.