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

The U.S. Food and Drug Administration asked Walmart to pull three lots of Great Value brand frozen shrimp from stores after federal officials detected Cesium-137, a radioactive isotope, in shipping containers and a sample of breaded shrimp imported from Indonesia.

The products could pose a “potential health concern” for people exposed to low levels of Cesium-137 over time, FDA officials said.

“If you have recently purchased raw frozen shrimp from Walmart that matches this description, throw it away,” FDA officials said in a statement.

The risk from the recalled shrimp is “quite low,” said Donald Schaffner, a food safety expert at Rutgers University.

Cesium-137 is a byproduct of nuclear reactions, including nuclear bombs, testing, reactor operations and accidents. It’s widespread around the world, with trace amounts found in the environment, including soil, food and air.

The level detected in the frozen breaded shrimp was far lower than FDA intervention levels. However, the agency said that avoiding potentially contaminated products could reduce exposure to low-level radiation that could lead to health problems over time.

The FDA is investigating reports of Cesium-137 contamination in shipping containers and products processed by P.T. Bahari Makmur Sejati, doing business as BMS Foods of Indonesia. U.S. Customs and Border Protection officials alerted FDA that they found Cesium-137 in shipping containers sent to U.S. ports in Los Angeles, Houston, Miami and Savannah, Georgia.

FDA officials collected several product samples and detected contamination in one sample of frozen breaded shrimp. The shipping containers and products were denied entry into the U.S.

However, the FDA then learned that Walmart had received potentially affected products imported after the first detection, from shipments that did not trigger contamination alerts.

Walmart immediately recalled the products, a company spokesperson said. They include Great Value brand frozen raw shrimp with lot codes 8005540-1, 8005538-1 and 8005539-1, all with best-by dates of March 15, 2027. The shrimp was sold in Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Missouri, Mississippi, Ohio, Oklahoma, Pennsylvania, Texas and West Virginia. Consumers should discard the products or return them to any Walmart store for refund.