The FDA has issued a warning to avoid Walmart’s Great Value raw frozen shrimp due to the presence of a radioactive isotope.

The FDA has recalled certain lots of Great Value brand frozen raw shrimp after they detected Cesium-137 in several shipments of the product. Cesium-137, or Cs-137, is a man-made radioactive isotope created during nuclear reactions.

The tainted shrimp were sold in stores in Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Missouri, Mississippi, Ohio, Oklahoma, Pennsylvania, Texas and West Virginia.

The FDA said they are working with Customs and Border Patrol to ensure none of the contaminated products reach consumers. So far, they’ve detected contaminated shipments in four U.S. ports.

Consumers are advised to throw away the recalled shrimp immediately and not to eat or serve it.