While companies were operating at a 1st alarm assignment on Nectarine Street, Box 1-4 sent county mutual aid to the 1200 block of Chestnut street for reports of a structure fire. Engines 30 (Penbrook), 37-1 (Rescue-Susquehanna Twp), Trucks 32 (Progress), 50 (Steelton) were dispatched at 0447 hours. Chief 1 (Enterline) enroute to Nectarine Street diverted to Chestnut Street and quickly arrived with a row of 3 dwellings off and requested a second alarm. Engine 40 (Paxtang), 2-13 (West Shore), Trucks 34 (Paxtonia), 12 (Lower Allen), Rescue 44 (Lawnton) and Air 30 (Penbrook) were sent on the 2nd alarm. Engine 30 and Truck 30 arrived as the fist due engine and truck company and set up on side A. Engine 37-1 and Engine 40 took a position on side C. Chief 1 reported possible entrapment but all occupants safely evacuated before first due units arrived. Several lines were stretch into the fire building and both exposures and a 2.5" step gun operated in the rear between the fire building and exposure B. The fire extended into the exposures A and D. Engine 2 (Harrisburg) responded to the scene with a crew along with Engine 32 which diverted from being special called to Nectarine Street. Units operated with an aggressive interior attack and knock the bulk of the down in about 20 minutes with extensive overhaul. Six occupants were displaced.