SEATTLE, Washington: A Seattle seafood company has expanded its recall of shrimp sold at Kroger grocery stores nationwide after U.S. regulators raised concerns about potential radioactive contamination.

Aquastar Corp. said over the weekend it was recalling nearly 157,000 additional pounds of cooked and frozen shrimp because of possible traces of cesium 137, a radioactive isotope. The affected products include almost 50,000 bags of Kroger Raw Colossal EZ Peel Shrimp, about 18,000 bags of Kroger Mercado Cooked Medium Peeled Tail-Off Shrimp, and more than 17,000 bags of AquaStar Peeled Tail-on Shrimp Skewers.

The shrimp was sold from June 12 to September 17 at more than a dozen Kroger-owned chains across 30 states, including Fred Meyer, Fry's, Ralph's, Smith's, King Soopers, and Mariano's. The company had already issued an earlier recall in August.

The U.S. Food and Drug Administration said the risk to consumers appears small, but warned the shrimp could pose a "potential health concern" if people are exposed to low levels of cesium 137 over time.

The FDA linked the issue to shrimp imported from an Indonesian supplier, PT. Bahari Makmur Sejati, also known as BMS Foods. In August, the agency detected cesium 137 in shipping containers and in one sample of breaded shrimp. While those shipments were not sold to the public, regulators said other batches processed under similar conditions may have been affected.

Officials believe contaminated metal near an industrial site in Indonesia may be the source of the radioactive material. The International Atomic Energy Agency said scrap metal disposal or smelting activity could be to blame.

So far, the FDA has blocked potentially contaminated shrimp from entering U.S. ports and issued an import alert for shipments from BMS Foods. More than 3 million pounds of the company's shrimp arrived at U.S. ports this month, according to Customs and Border Protection.

The radioactive levels detected were about 68 becquerels per kilogram, far below the FDA's threshold of 1,200 becquerels per kilogram that would trigger health protections. Still, experts urged authorities to identify the exact source of the contamination and keep the public informed.