The Food and Drug Administration (FDA) has issued a new warning about thousands of recalled eggs sold at Costco (COST) stores due to potential contamination with salmonella, a bacterium that can cause serious infections. The recall has been elevated to the FDA’s highest risk level.

In November, Costco recalled nearly 260,000 eggs sold under the Kirkland Signature brand in 25 stores nationwide. The eggs landed on shelves in Alabama, North Carolina, Georgia, South Carolina and Tennessee starting Nov. 22, according to the company.

The FDA has classified its recall of eggs sold under Costco's Kirkland brand as a Class I recall, a designation reserved for instances of the highest potential health risk — including death.