Advanced-Connectek has made unglamorous but critical computer components for Apple for more than a decade. For two of those years, it operated a factory inside an industrial park on the edge of the deserts of Xinjiang, a region of western China populated by a predominantly Muslim group known as Uyghurs. The industrial park is surrounded by walls and fences with only one way in or out.

And next to the park was a large compound identified by a satellite imagery researcher as a detention center where the factory workers lived. The researcher, Nathan Ruser, from an Australian think tank, said “almost no other factories in Xinjiang have these characteristics except for industrial parks where there is detainee labor.”

The Information and human rights groups have found seven companies supplying device components, coatings and assembly services to Apple that are linked to alleged forced labor involving Uyghurs and other oppressed minorities in China. At least five of those companies received thousands of Uyghur and other minority workers at specific factory sites or subsidiaries that did work for Apple, the investigation found.

The revelation stands in contrast to Apple’s assertions over the past year that it hasn’t found evidence of forced labor in its supply chain.