The FDA has issued an update on the seafood detected to have some contamination with Cs-137. See: https://www.fda.gov/food/alerts-advisories-safety-information/fda-advises-public-not-eat-sell-or-serve-certain-imported-frozen-shrimp-indonesian-firm. The FDA also issued an Import Alert 99-51 on the plant that introduced the contamination in the food product. See: https://www.accessdata.fda.gov/cms_ia/importalert_1187.html.
Food impounded under this type of action normally cannot be released after testing, even if there is no indication of contamination in the product that was seized.
The levels detected in the shrimp were very low (68 Bq/kg Cs-137), The limit, called the Derived Intervention Level (DIL), is 1250 Bq/kg for Cs-137 in food products. No information has been given as to how Cs-137, a man-made isotope, found its way into a food processing plant.