ATCHISON, Kan. (AP) — The federal government has cited a grain company for willful safety violations in a northeast Kansas elevator explosion that killed six workers last October. U.S. Labor Secretary Hilda Solis said in a news release Thursday the deaths at the Bartlett Grain Company elevator in Atchison "could have been prevented" if the operators had addressed hazards known in the industry. Kansas investigators previously determined the October 29, 2011, grain dust explosion was accidental. A release from the labor department notes that grain dust is nine times as explosive as coal dust. The agency said problems included a lack of proper preventive maintenance and an inadequate emergency action plan. The president of Kansas City, Mo.-based Bartlett Grain, Bob Knief, said in a statement that the company "adamantly" disagrees with the claims.