UNION MILLS, Ind. (AP) _ Investigators say an overheated motor in a grain silo ignited dust and caused a blast that killed a worker at a northwestern Indiana business earlier this week.
 
  Chief Deputy James Sosinski tells The LaPorte County Herald Argus that investigators from the Bureau of Alcohol, Tobacco, Firearms and Explosives and the Indiana Fire Marshal’s office found scorched motors in the basement and on the decking of the silo at the Union Mills Co-op. He says both motors were experiencing drops in voltage before the explosion, and one or both appear to have overheated.
 
  Sixty-seven-year-old James M. Swank of Union Mills died in the blast. He had worked at the co-op for seven years.
 
  LaPorte County Coroner John Sullivan says Swank died from blunt force trauma caused by the explosion.