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.

“To date, FDA has learned that Walmart has received implicated raw frozen shrimp, imported after the date of first detection of Cs-137 by CBP [Customs & Border Patrol], but from shipments that did not alert for Cs-137,” the statement noted.