Allentown Comm Center transmitted the box for an apartment fire with an address of 2635 Prospect Avenue in Apartment 8 sending Engines 11, 14, 10, Tower Ladder 1 and Battalioin Chief 3 (G. Scheirer). Enroute, police transmitted "fire showing." Phone calls report possible people trapped. Engine 11 arrives and transmits "a working fire" in a two-story garden-style apartment building fully occupied. BC 3 arrives while engine crews are stretching into the stairwell to the top floor. BC 3 proceeds to the rear for a size-up and finds heavy fire venting from all the windows and roof. He strikes the second alarm and orders the interior crews out of the building. Engines 4, 6, 9 (safety), Air 1, FM 4, 47 and 48 respond. Larger handlines and stangs are put into service along with the squirt and tower ladder. As the fire engulfs the roof and then collapses, BC 3 strikes the third alarm. Engine 13 and Ladder 2 respond. All Hands are now working at this location. 7 families are homeless. One firefighter sustained minor injuries from a fall on ice. The temperature was 17'F with a wind chill of 3'F.