At least one person was injured and 20 families displaced after a three-alarm fire broke out at an apartment building in the Bronx.

The fire started around 8:15 p.m. Sunday inside the top floor of an apartment building at 1038 Southern Blvd. in Longwood. 

Fire officials say an 85-year-old woman was transported to Lincoln Hospital in critical condition.

The American Red Cross says 20 families were displaced in the fire and that one unit was completely destroyed while 18 others were evacuated. The group is assisting the displaced families, Red Cross officials say. 

The cause of the fire is being investigated.