Michigan residents are being urged not to consume a brand of romaine lettuce sold at Walmart stores after it tested positive for E. coli. The Michigan Department of Agriculture and Rural Development (MDARD) warns Michigan consumers that single heads of romaine lettuce sold by the brand Tanimura & Antle have tested positive for a strain of E. coli. Anyone who purchased the product, sold at Walmart stores, is urged to throw it away or return it at the point of purchase for a full refund. The lettuce heads were sold in a zip-top clear plastic bag with a blue label and white lettering, officials said. Symptoms of an E. coli infection can include severe stomach cramps, diarrhea (often bloody), vomiting and sometimes a fever.