Federal officials are working with Nebraska Beef Ltd. to improve food safety after the company recalled more than 5 million pounds of meat.

USDA spokeswoman Amanda Eamich said Monday the company was slow to respond to reports that two samples at processors that bought the meat from Nebraska Beef had tested positive for E. coli.

The meat Nebraska Beef produced between May 16 and June 26 has since been linked to an outbreak of E. coli illnesses affecting 41 people in Michigan and Ohio.

Nebraska Beef spokesman Bill Lamson said the company has hired an outside lab to test company products as it moves ahead with the recall.

The E. coli 0157:H7 variant can cause severe illness and even death in humans.