The building is located in the 800 block of Delmas Avenue.
Firefighters battled the flames as smoke poured out a second-story unit.
The residents of the unit had left about an hour earlier.
It took 20 minutes for crews to put the fire out.
Firefighters believe it began in a bedroom.
Extensive smoke and water damage to the entire building forced all 17 residents to find somewhere else to stay.
No injuries were reported.