A collision between a double-decker bus and a city bus in Manhattan on Thursday left dozens injured and at least 18 people requiring hospitalization for non-life-threatening injuries, according to the New York City Fire Department.

First responders received notice of the crash on the borough's east side shortly after 7 p.m. Thursday, said FDNY Deputy Chief Kevin Murphy.

"The first two units arrived to find two buses involved in what appeared to be a serious accident, complicated by the fact that one of them was a double-decker bus," Murphy said at a news conference at the scene.

Ropes and ladders were used to assist passengers with getting off the buses, officials said.

"Any time you have two buses involved you have a significant number of patients that likely need to be treated," Murphy said. "So seeing that quantity of people right away, I think the units did a very good job getting them off the bus quickly and taken to the appropriate resources."

Eighteen patients were transported to area hospitals but none have life-threatening injuries, the fire department said.

"Many injuries are just cuts, bruises, scrapes, some suspected fractures. Some head and neck injuries as well," said Deputy Chief Paul Hopper. "We're all quite fortunate it was not much worse."

Another 63 people were needing assessment from a fire department doctor, Hopper said, adding, "We expect that they will refuse medical attention and be seen by our doctor who is on the scene and on the bus evaluating patients."

It is not yet clear what caused the crash, fire officials say.

A spokesperson for the Metropolitan Transportation Authority said there was a crash at 7:17 p.m. on bus route X27 and referred CNN to the fire department for further details. Police referred CNN to the fire department when asked for comment.