Authorities are investigating a fire that destroyed a Cumming business Wednesday afternoon.According to Capt. Jason Shivers of the Forsyth County Fire Department, Benton Motorsports at 328 Dahlonega St. was engulfed in flames when firefighters arrived.Shivers said the cause is unknown.“It’s under investigation already,” Shivers said. “Initially, there’s nothing about it that seems suspicious, but of course we’re going to look into it thoroughly.”The business owners were inside, he said, when they smelled smoke and evacuated the building.No one was injured, Shivers said.“We were able to salvage some part of the front offices,” he said, “but beyond that, it’s going to be a significant loss of the structure and its contents.”Also, 11 vehicles were lost or damaged in the fire, he said.Within the first 20 minutes, he said the 30 responding firefighters had the blaze under control.The stretch of Dahlonega Street was blocked off to traffic in both directions until about 5 p.m. because the water supply line had to be stretched across the street.Firefighters worked through heat and then thunderstorms, Shivers said.“Everybody assumes that rain helps fire. It doesn’t,” he said.