Fire officials say the Saint Nicholas Avenue building where the fire started shortly before 11 a.m. has both commercial and residential occupants, though it wasn't clear if any homes were damaged in the blaze.
The fire escalated to four alarms shortly before noon. Fire officials say the seriously injured firefighter was taken to the hospital and is expected to survive. One firefighter was treated at the scene, and a third injured firefighter refused medical attention.
Two civilians were also injured. Both were treated at the scene.