A fire at a Milwaukee U-Haul storage complex in April likely began when electrical wiring near a generator system malfunctioned, investigators say. The system had been installed after a January fire left part of the property without electricity. The Milwaukee Fire Department report says investigators could not rule out “negligence or reckless conduct” in how power was routed through the building. It does not make a final determination: the cause of the April 6 fire remains listed as under investigation, as does the cause of the January blaze. The fires occurred less than four months apart at the complex on South 1st Street in the Harbor View neighborhood. The Jan. 21 fire destroyed a one-story building at 1500 S. 1st St. The April fire heavily damaged a connected, four-story storage building at 1574 S. 1st St. No injuries were reported in either fire. Investigators said the April fire probably started on the first floor, in the northeast corner of the building, among metal storage units. They found signs of electrical arcing and fire damage on exposed wiring that had contacted metal unit walls, near conduit connected to the generator setup. According to the report, We Energies declined to restore service to the damaged building after the January fire. Property owner Sean Breske told investigators he hired Nelco Electric, a Germantown contractor, two days after that fire to connect three 150-kilowatt generators to the property’s existing electrical panel. Two generators powered areas during business hours; a third ran continuously at a loading dock to keep a key-fob entry system working for renters. The report also documents multiple safety concerns at the building, including defective wiring, exposed extension cords and improper storage of combustible materials. Investigators said smoke detectors and the fire alarm were not working, the sprinkler system did not activate, and the building had not been reinspected before operations resumed after the January fire. The first fire was reported at 6:38 p.m. Employees told investigators they heard sounds like fireworks, then found flames upstairs and evacuated. The April fire was reported by multiple callers beginning at 8:56 p.m. Firefighters initially attempted an interior attack but withdrew after low-air alarms sounded amid heavy smoke and heat.