Walmart has recalled frozen, raw shrimp sold in 13 U.S. states because federal health officials say it could have potential radioactive contamination.

The FDA detected Cesium-137, a radioactive isotope, in one shipment of Great Value frozen raw shrimp to Walmart. It said the affected shipment wasn’t sold.

Some packages of Great Value frozen shrimp sold at Walmart are at risk for potential for Cesium-137 contamination, the FDA says.