U.S. Customs and Border Protection officers detained a shipment of almost 13 tons of wigs and other human hair products suspected of being made through forced labor in Xinjiang, China, U.S. government officials tell Axios.Why it matters: Importing products made with forced labor into the U.S. is illegal. But it's extremely difficult to trace U.S. supply chains back to factories in Xinjiang that use forced labor, making this a rare event.What's happening: On June 17, CBP issued a withhold release order for Lop County Meixin Hair Product Co. Ltd. in southern Xinjiang requiring U.S. ports of entry to detain any shipments from that company to the U.S.CBP officials at the Port of New York/Newark subsequently detained the shipment of Meixin Hair Product goods, which included wigs and other human hair products.A withhold release order indicates CBP has uncovered strong evidence linking those products to forced labor. Once their goods are seized, the importing company is given the opportunity to provide proof that the products are not made with forced labor. What they're saying: “The production of these goods constitutes a very serious human rights violation, and the detention order is intended to send a clear and direct message to all entities seeking to do business with the United States that illicit and inhumane practices will not be tolerated in U.S. supply chains," Brenda Smith, executive assistant commissioner of the CBP Office of Trade, said in a statement.“If this highly suspicious, 13-ton shipment of human hair indeed turns out to be linked to the Uighur concentration camps, then this is a new low — even for the Chinese Communist Party — and they will have to answer to the world community for their actions,” National Security Council spokesperson John Ullyot tells Axios. The Chinese embassy in Washington, D.C. did not respond to a request for comment.Background: The Chinese government has instituted forced labor on a mass scale as part of its campaign to subjugate and forcibly assimilate Uighurs and other Muslim ethnic minorities.More than a million Uighurs have been detained in a string of concentration camps in Xinjiang. Some former detainees are sent to work in factories, where they are under tight surveillance and may be forced to attend indoctrination sessions.Numerous female survivors have said women's heads were shaved when they were admitted to the camps.The big picture: Trump administration officials have repeatedly condemned China's repression of Uighurs, though President Trump himself has downplayed it.The National Security Council has placed a strong focus on China's treatment of Uighurs and hired a Uighur-American to serve as a China director at the council.Go deeper: The U.S. has the tools to fight Uighur forced laborCaterpillar sourced clothes from Xinjiang factory involved in coercive labor