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.

The FDA classified a November recall over potential salmonella contamination for eggs sold at Costco at its highest risk level.

Federal food regulators raised their alarm for recalled eggs sold from Costco stores over possible salmonella exposure, reclassifying the targeted product to its highest risk level.