A Wisconsin grain mill operator is contesting a one-point-eight-million dollar fine proposed by the U-S Department of Labor. Officials at Didion Mills in Cambria say the federal penalties are too severe. Five people were killed and 12 others injured in the May 31st explosion at the central Wisconsin plant. The Occupational Safety and Health Administration says Didion failed to correct a leakage of highly-combustible grain dust — and didn’t properly maintain its equipment to control ignition sources. The Department of Labor announced the fine Friday. Didion has 15 days to respond.