The fire broke out shortly after 10:00 p.m. on the first floor of a three-story house on the 300 block of Washington Street.
Firefighters arrived to find heavy smoke and flames coming from the building, which houses several sub-divided apartments. Additional crews were called in to assist.
The fire was placed under control within two hours.
Two firefighters were treated for exhaustion, and medics treated several residents at the scene.
Officials say seven people were displaced. The Red Cross is assisting with housing.
Investigators were trying to determine what sparked the blaze.
Damage to the building was estimated to be about $150,000.