Beef supplier Nebraska Beef Ltd. is recalling over 500,000 pounds of ground beef it produced in the last two months because the meat has been linked to an E. coli outbreak in Michigan and Ohio that has triggered lawsuits against The Kroger Co.

The U.S. Department of Agriculture's Food Safety and Inspection Service said the beef supplier was identified as the source of meat implicated in the E. coli outbreak, which is suspected as the cause of at least 38 confirmed illnesses in Michigan and Ohio. As a result, Nebraska Beef is recalling about 531,700 pounds of ground beef that may be contaminated with the E. coli 0157:H7. USDA assigned the situation as a Class I recall, which means it carries a high health risk.

Investigators traced the meat to Nebraska Beef after several people in Ohio and Michigan became ill in central Ohio in mid-June amid a sharp increase in E. coli cases around the same time in Michigan. By June 20, officials had genetically linked many of the Ohio and Michigan cases to ground beef purchased from Kroger stores.

Kroger had already issued its own recall of beef, with sell-by dates of May 21 to June 8, that it sold in both Michigan and Ohio.

However, Nebraska Beef said it distributed some of the contaminated products also to accounts in Illinois, New York, and Pennsylvania, while additional beef products were sent to Colorado and Texas for further processing. It was not immediately clear whether potentially contaminated beef was also sold in other stores those states.

Government investigators expect more illness reports to follow, as the Centers for Disease Control and Prevention estimated that for every reported E. coli incident, 20 go unreported.