A tomato recall affecting three southern states has been upgraded to a Class I recall, the most severe warning by the Food and Drug Administration. The recall of the tomatoes was first announced in May over potential salmonella contamination.

Class I is the FDA’s highest recall designation for health hazards, meaning there is “a reasonable probability” that the product will cause “serious adverse health consequences or death.”

The tomatoes, from Williams Farms Repack, LLC, were shipped to Georgia, North Carolina and South Carolina. The impacted products include a 3 count package, 10 pound box, 25 pound box as well as a 60 count 2 layer box, the FDA says.

The FDA is urging consumers who purchased these products not to consume them, adding they can return them to the place of purchase for a full refund or discard them.

Salmonella can cause “serious and sometimes fatal infections in young children, frail or elderly people, and others with weakened immune systems,” the FDA wrote in its initial recall announcement.

Healthy people infected with the bacteria often experience a range of symptoms, including: fever, diarrhea, nausea, vomiting and abdominal pain.

According to the Centers for Disease Control and Prevention, symptoms usually start six hours to six days after consuming the bacteria.

Most people recover without treatment after four to seven days, but younger children, older adults and those with weakened immune systems “may experience more severe illnesses that require medical treatment or hospitalization,” the CDC says.