At 0025 hours, Box Alarm 14-70 sent Engines 14, 36, 8 (RIT), 30, 23, Trucks 10, 8, Rescue 1, and Battalion Chiefs 3, 6 to W. Pratt and Harmison Streets for the building fire. Communications also were receiving W. Pratt and S. Payson Streets. Squad 26, in the area on fire watch due to an arson spree in Company 14’s area, had smoke in the area, and after further investigation had fire to the rear of 2021-2023 Frederick Avenue. Squad 26 stretched a line down Harmison Street to put a knock on heavy fire but with limited access. Engine 14 stretched an alley line from the Pulaski Street side. Air Flex 1 added to the box at 0028 hours. Companies had a collapse in the rear and live electrical lines. Additional companies made entry from the Frederick Ave. side to check for extension which was minimal. 3 lines stretched and operated and the fire was placed under control in about 30 minutes.