Crews acted quickly to put out a fire at the NYU Langone Medical Center Wednesday.
Officials say flames broke out on the seventh floor of the Kimmel Pavilion, which is a new facility set to open in 2018.
The Fire Department says it started when construction material located on the roof ignited.
There were no reported injuries, but people working inside the building had to evacuate.
"I just dropped my tools and went and grabbed my bag and headed for the stairwell," said one worker. "And I get to the stairwell, there's guys filing down from the floors above. Everybody's just kind of wondering what the deal is. What's going on."
"This is rigid board used for insulation, used for roofing insulation," said FDNY Deputy Assistant Chief Michael Gala.
QUESTION: So this is what caught fire?
"This is what was on fire yes," Gala said
QUESTION: And this is highly flammable I take it?
"It's highly flammable," the chief said.
The Medical Center says no patients were in the building, and that the fire is not affecting patient care.
Officials say very limited smoke entered the hospital.