Fire investigators are attempting to determine what caused a blaze Wednesday that damaged a vacant home in North Forsyth County.A passing motorist reported the fire about 5 p.m. Fire Division Chief Jason Shivers said firefighters arrived at the A.C. Smith Road home within three minutes.“In about eight minutes we had the fire under control,” Shivers said. “Fortunately, it was about a mile from Station 7, so they had a very rapid response.”The road was closed to traffic for a couple of hours so firefighters could access the water supply. No one was injured in the blaze, which at one point covered about a quarter of the one-story home, Shivers said.He added that the home had been “lived in recently,” but was vacant at the time.