U.S. Customs and Border Protection (CBP) began detaining merchandise produced by three Chinese companies in early December after finding the companies used North Korean labor in violation of federal law, the agency has announced.

The CBP said in a press release last Tuesday that it started implementing the restrictions on items from Jingde Trading Ltd., Rixin Foods Ltd. and Zhejiang Sunrise Garment Group Co. Ltd. at all U.S. ports of entry starting Dec. 5.

The agency did not provide further details about the companies or their actions that resulted in the ban, but a U.N. Panel of Experts report in