The fire began just after 12 p.m. on the seventh floor rooftop of a building under construction on NYU Langone Medical Center's East Side campus at 34th Street and First Avenue. Firefighters had it under control by 12:45 a.m.
The building is the Kimmel Pavilion, which is next to the main hospital building. Construction began three years ago and the building is expected to open in 2018.
A spark from a worker cutting metal caused the fire. Building materials laid out on the roof helped the fire to spread quickly.
Video shows flames shooting from the building:
Smoke from the fire could be seen for miles. Eyewitness News viewers posted photos showing the smoke from all over the city.
See photos here:
NYU moved patients from areas impacted by smoke to other areas within the hospital.
"As a precaution, some patients in rooms on the north side of Tisch Hospital facing the construction were moved to the south side of the floor. They have since been located back to their rooms," NYU Langone said in a statement.
"Firefighters were quickly able to get to the seventh floor, stretch a few hundred feet of hose and did a great job extinguishing this fire quickly," FDNY Commissioner Daniel Nigro said.
No one was hurt in the fire.
Here's a look at the aftermath of the fire: