PEORIA FLATS — Central South Dakota firefighters are working to put out a major wind-drive grass fire north of Pierre. The fire is west of state Highway 1804 near 199th Avenue, about four miles south of the Hughes/Sully County border. Hughes/Stanley County Emergency Manager Rob Fines says that as of four pm the fire had burned an estimated 350 acres of crop land and an additional 80 acres of grass. Fines says no homes or structures were lost. A plume of smoke extended from the fire southeast blocking views of the Oahe Dam and down the Missouri River and drifting just east of Pierre. Fire Departments from Fort Pierre, Onida, Murdo, Pierre and other cities are assisting the Pierre Rural Fire Department. A High Wind Warning and Red Flag Warning were both in place for Hughes County at the time. The South Dakota Highway Patrol on Facebook asked people to stay away from Highway 1804 to allow fire crews space to work. A trooper was also blocking non-fire traffic from 199th Avenue. Numerous onlookers were seen stopping on the side of the highway or many of the overlooks above Oahe to get a view of the cloud wall as it accelerated southeast. The cause of the fire is unknown.