UNION MILLS, Ind. (AP) _ The owners of a northwestern Indiana grain elevator that exploded and killed a worker say an investigation is focusing on grain dust ignition as the cause of the blast.
 
  Co-Alliance LLP, a farmers cooperative that owns the Union Mills Co-op in LaPorte County, also said Tuesday that “preliminary indications are that an explosion took place at the top of the grain elevator.”
 
  The blast Monday afternoon killed 67-year-old James Swank of Union Mills, a town located about 50 miles southeast of Chicago. Co-Alliance says Swank had worked at the co-op for seven years. No other injuries were reported.
 
  The U.S. Bureau of Alcohol, Tobacco, Firms and Explosives is among the agencies investigating the explosion.
 
  Co-Alliance says it arranged for grief counselors to visit the co-op Tuesday.