Indonesia has halted imports of scrap metal after tracing radioactive contamination found at an industrial site and in shrimp shipments to the U.S. to local metal processors.

The suspension is effective immediately, Bara Krishna Hasibuan, an official with the government task force investigating the radiation findings, said in a text message Thursday.

Environment Minister Hanif Faisol Nurofiq said the pause aims to ensure that the local steel-recycling industry meets radiation safety standards, with companies required to install radiation monitoring and emission-control systems, state news agency Antara reported.

The import halt follows an investigation into findings last month of cesium-137 at a metal-processing hub of an industrial park in western Java that supplies materials for construction and manufacturing. The probe was initiated after the U.S. Food and Drug Administration in August reported the detection of trace amounts of the radioactive material in frozen shrimp shipments from one of Indonesia’s largest prawn companies, leading to recalls by companies such as Walmart.

The shrimp company, PT Bahari Makmur Sejati, has facilities near the contaminated sites of the industrial park.

The government task force said Wednesday that authorities had identified radiation at 22 production facilities in the industrial zone, with one since decontaminated and the remainder undergoing cleanup.

It said two containers of shrimp products suspected of contamination have arrived back from the U.S., with one undergoing testing and the other still in port. Another 29 returned by the U.S. as a precaution — known as "return-on-board” shipments — have been found free of radioactive material and returned to local companies, the task force said.

It also said the maritime affairs and fisheries ministry had agreed with the FDA to draft a memorandum of understanding on shrimp safety certification to help Indonesian exporters maintain access to the U.S. market.

Cesium-137 is an artificial radionuclide used in medical devices and gauges, and is also one of the byproducts of nuclear fission processes in reactors and weapons testing. Exposure to the isotope can raise the risk of cancer, according to the U.S. Centers for Disease Control and Prevention.

The task force said nine people found contaminated with the isotope have all recovered and been discharged from medical facilities. It added that it is still investigating U.S. findings of contamination in a shipment of cloves from a company based in eastern Java.