MANHATTAN, N.Y. — A 91-year-old mother and her 52-year-old son were killed and several others, including two firefighters, were injured in a fire at a Chinatown apartment building Friday, officials said.

FDNY crews were called to the six-story residential building on Mulberry Street, near Canal Street, just after 3:45 a.m.

Authorities said the fire was located on the fifth floor, and had spread into the hallway and public areas of the building.

The blaze quickly rose to two alarms with more than 100 fire personnel responding to the scene.

It took one hour to bring the fire under control, according to FDNY Chief Michael Ajello, who noted that cluttered conditions in the building made it difficult for firefighters to search the building.

One person was pronounced dead at the scene, officials said. A second person who was discovered critically injured inside the building was also pronounced dead at a nearby hospital.

They victims were later identified as a mother and son who lived in the building.

Ajello told reporters that two other residents in the building suffered minor injuries, as well as two firefighters.

The FDNY chief said one firefighter was injured after falling partially through a half-landing inside the building. He noted that the aging stairways inside the building had become unstable as the situation progressed.

The cause of the fire remains under investigation and authorities could not confirm if there were smoke alarms in the building at the time of the fire.

According to the Red Cross, nine households were registered for housing assistance in the aftermath of the fire and a total of 34 units were evacuated.

The humanitarian group said some of the units were vacant and some residents were not home at the time of the fire. Several others in the building did not ask for assistance.