Beloit fire officials are investigating the cause of a residential fire on the city’s east side. Battalion Chief Todd Farley says firefighters were called out shortly before 4:30 a.m. Wednesday to a two-unit, two-story home in the 800 block of Wisconsin Avenue. Farley says crews arrived to find flames showing through the roof. Farley says the difficulty in fighting the attic fire prompted them to call in additional help from the Town of Beloit, Janesville, Harlem Roscoe, and Footville departments. He says firefighters were on the scene for four-hours. Residents of both units escaped safely and Farley says the Red Cross is assisting the families. He adds damage is considered extensive.