The agency said the region-wide ban was "based on information that reasonably indicates the use of detainee or prison labor and situations of forced labor," saying it had found examples of debt bondage, restriction of movement, isolation, intimidation and threats, withholding of wages, and abusive living and working conditions.
The State Department estimates that more than 1 million Uyghurs, as well as members of other Muslim minority groups, have been detained in a sprawling network of internment camps in Xinjiang. Accounts of abuse at the camps are numerous.
Beijing has denied accusations of mistreatment, and says it's providing vocational training and helping to deradicalize segments of the population to combat alleged Islamic terrorism and violence.
"CBP will not tolerate the Chinese government's exploitation of modern slavery to import goods into the United States below fair market value," the agency's Acting Commissioner Mark A. Morgan said in a statement.