U.S. Customs and Border Protection detected Cs-137 in shipping containers at four ports in the United States. The FDA tested a sample of frozen shrimp from Indonesia’s BMS Foods, which came back positive for Cs-137. No shrimp that has tested positive for Cs-137 has entered the U.S. food supply, per the FDA.

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

Update, August 22, 7:04 am EDT: On August 21, the FDA expanded its recall to include raw and cooked frozen shrimp products sold by Southwind Foods, LLC. The FDA and Southwinds Food said that the company is “voluntarily recalling a limited quantity of frozen shrimp” due to possible contamination with Cesium-137.