Hundreds of boxes of blueberries are being recalled due to the possibility of being contaminated by listeria, according to the Food and Drug Administration.

Alma Pak International LLC, issued a voluntary recall on June 9 for 400 boxes of its organic blueberries. On July 1, the FDA classified the recall as a Class I risk, which is the highest class level.

This means the recall is “a situation in which there is a reasonable probability that the use of or exposure to a violative product will cause serious adverse health consequences or death,” according to the FDA.

Listeria is “an organism which can cause serious and sometimes fatal infections in young children, frail or elderly people and others with weakened immune systems,” the administration explained.

“Although healthy individuals may suffer only short-term symptoms such as high fever, severe headache, stiffness, nausea, abdominal pain and diarrhea, listeria infection can cause miscarriages and stillbirths among pregnant women.”

In total, 400 boxes, each weighing 30 pounds, are being recalled. The blueberries were shipped to a customer in North Carolina and have the lot numbers 13325 G1060 and 13325 G1096.

The reason for the recall was that listeria was found on one of the company’s finished products during routine testing of the firm, the administration’s website reads.