It broke out at 1:00 p.m. Wednesday at a home at the intersection of Venango and Randolph Streets.
Officials say firefighters arrived to find heavy fire coming from a first floor apartment.
Images from Chopper 6 HD over the scene showed a 3-story home with smoke pouring from a first floor window.
Several fire trucks were on the scene and firefighters were working on the roof.
There were no immediate reports of injuries or a possible cause.