Federal prosecutors say there is not sufficient evidence to charge the owner of a northeast Kansas grain elevator where a 2011 explosion killed six people and injured two others.

U.S. Attorney Tom Beall said in a statement Thursday that his office has closed its inquiry into the Oct. 29, 2011, explosion at the Bartlett Grain Co. elevator in Atchison, about 50 miles northwest of Kansas City.

Kansas investigators previously determined the grain dust explosion was accidental.

The announcement does not dismiss pending enforcement actions by the Occupational Safety and Health Administration, which has said the deaths could have been prevented had operators addressed known industry hazards.

The explosion killed Bartlett employees John Burke, Ryan Federinko, Curtis Field, and Chad Roberts, as well as grain inspectors Travis Keil and Darrek Klahr.