Fire Department spokesman Brian Humphrey says the fire was reported in a third-floor unit at about 10 a.m. Wednesday and 171 firefighters brought it under control 83 minutes later.
Firefighters used ladders to rescue two people from a third-floor balcony.
Humphrey says one resident was taken to a hospital for treatment of smoke exposure that was not life-threatening.
The building is being assessed by safety inspectors. The building was initially believed to be a condo complex, but Humphrey says the units are apartments.