Although there’s been no confirmation of radiation risk in food purchased at Walmart stores, the FDA said that it has detected unsafe levels of cesium-137 contamination at four U.S. ports. This contamination likely suggests that the shrimp was packaged in unsanitary conditions.

The US Food and Drug Administration on Tuesday urged the public not to eat certain bags of frozen raw shrimp sold at Walmart, citing concerns about unsanitary conditions and radioactive contamination found in shipments from the same supplier.

The warning is for some Great Value raw frozen shrimp because it may be contaminated with Cesium-137, a radioactive isotope.