short answer: https://en.wikipedia.org/wiki/Xinjiang_re-education_camps "As of 2018, it is estimated that the Chinese authorities may have detained hundreds of thousands, perhaps a million, of Uyghurs, Kazakhs, Kyrgyz, Hui (Muslims) and other ethnic Turkic Muslims, Christians as well as some foreign citizens such as Kazakhstanis, who are kept in these secretive internment camps throughout the region."