An Arlington County bomb squad technician and an Arlington County firefighter confer in the apartment where the three-alarm fire began on Jan. 5. (Katherine Frey/The Washington Post)

Residents of a seven-story Arlington County apartment complex leapt from windows to escape the flames and smoke of a three-alarm blaze on South Greenbrier Street near Columbia Pike on Sunday morning.

County officials said that the firefighters arrived on the scene around 9:30 a.m. Sunday to douse the blaze that started in a second-floor apartment at the Harvey Hall Apartments at 850 S. Greenbrier St. More than 90 firefighters from Arlington, Fairfax County and Falls Church city responded to the scene.

Firefighters used ladders to rescue residents from the burning building, which was evacuated. Officials said that multiple victims were treated for injuries related to the fire. One man was transported to the MedStar Washington Hospital Center with life-threatening injuries, Arlington fire officials said. A second person, who was already on oxygen, was taken to the hospital as a precaution.

The affordable housing complex is home to 116 families and also houses senior citizens, said Catherine Bucknam, director of community relations for AHC Inc., which owns the building.

The second and third floors of the building were heavily damaged by the fire, officials said. Three units were declared uninhabitable due to smoke and water damage, Bucknam said, and the Red Cross was on scene to help displaced residents find temporary housing. Most residents will return home by the end of the day Sunday, Bucknam said.

The cause of the fire remains under investigation, officials said.