Auditors from five different certification organizations have said they will not help companies verify their supply chains in China’s Xinjiang region due to the difficulty of determining whether the supply chains are relying on forced labor from Muslim minorities, particularly ethnic Uighurs, according to the Wall Street Journal.

The presence of internment camps in the province has become the source of major human rights complaints, including from the United States, leading several companies to pledge that they will not source their supplies from that region. Such pledges, if they are to mean anything, usually require audits to ensure compliance. But the organizations that provide these audits, generally rights-based non-governmental organizations, said they cannot provide such assurance on this matter, as a heavy police presence means that inspecting factories and other facilities with any degree of independence is next to impossible.

The five organizations are France's Bureau Veritas, Germany's TÜV SÜD AG, Italy's RINA SpA, plus Sumerra LLC and the Worldwide Responsible Accredited Production, the last two based in the United States.

The Journal said that the Chinese government has detained auditors trying to conduct inspections in the region, and it is mandating a state-appointed interpreter, who might lie to the auditors. Further, even if the auditors could get interviews with the workers, those workers might be hesitant to fully explain their situation, out of fear of reprisal.