A three-alarm fire broke out in an apartment building in Brooklyn on Tuesday night, injuring four first responders, officials said.

The blaze at 910 Bergen St. in Crown Heights started at 9:18 p.m. and spread to a neighboring building.

All residents of both buildings got out safely.

Three firefighters and one cop were taken to hospitals, and all will be OK, officials said.

The fire started on the second floor of 910 Bergen before spreading to the third floor.

“We did have a problem with our members going up the stairs. The stairs gave way, and we had three firefighters hurt on the stairway — not serious injuries,” FDNY Assistant Chief Roger Sakowich said.