CHICAGO (Reuters) - A Colorado meat company is expanding a recall of beef due to possible contamination by E.coli O157:H7 bacteria after an investigation found 18 illnesses may be linked to the meat, the company and the U.S. Agriculture Department said on Sunday.

Greeley, Colorado-based JBS-Swift Beef Co is voluntarily expanding its June 24 recall to include about 380,000 lbs of assorted beef products, for a total recall of about 421,000 lbs, USDA and the company said.

The affected beef was produced on April 21 and was distributed nationally and internationally.

“The contamination may have come from further processing by other companies,” Chandler Keys, JBS spokesman, said on Sunday.

USDA said the recalled products are typically used for steaks and roasts rather than ground beef. However, it said some of the beef may have been processed into ground products by other companies.

It is unlikely the recall will be expanded further, and JBS will be contacting customers that received the beef to learn how the product was distributed, said Keys.

The contamination was investigated by USDA’s Food Safety and Inspection Service in cooperation with the Centers for Disease Control and Prevention.

E.coli O157:H7 is a potentially deadly bacteria that can cause bloody diarrhea, dehydration, and, in severe cases, kidney failure. The very young, seniors, and persons with weak immune systems are at the most risk.

Consumers with questions can call 1-800-685-6328.

JBS Swift is a unit of Brazilian meat company JBS S.A.