A two-alarm fire at an apartment building in Capitol Hill has been knocked down, D.C. fire officials said Thursday night.

Firefighters got a call of a fire on the third floor of a six-story apartment building in the 1200 block of G St. SE. about 7:45 p.m. There was heavy smoke coming from an apartment on the third floor, said Pete Piringer, a fire department spokesman.

Firefighters rescued at least four people by ladder from the third floor, and helped about two dozen people evacuate the building, which has many seniors as residents.

Piringer said one firefighter was injured, but the extent and nature of the injury was not immediately known.

The fire was extinguished in about a half hour, but eastbound lanes of nearby Pennsylvania Avenue SE in the area were still closed at about 8:30 p.m.