Canada’s corporate watchdog will probe Walmart, Hugo Boss and clothing brand Diesel following allegations the companies exploited the forced labour of China’s ethnic minority Uighurs.

The Canadian Ombudsperson for Responsible Enterprise (CORE) announced its investigation on Thursday after civil society groups last year accused the firms of using Chinese suppliers implicated in forced labour in Xinjiang.

The probe comes after the three companies, which have denied accusations of using forced labour, refused to participate in a preliminary assessment of the claims.

“As mediation between the parties is not currently an option, we will be launching investigations into the allegations outlined in these reports,” CORE spokesperson Sheri Meyerhoffer said in a statement.

“The investigations will provide all three companies with an ongoing opportunity to provide further relevant information and mediation of the allegations remains open.We are hopeful that the investigation findings will provide the companies with information to support their ability to strengthen their due diligence practices.”

Walmart, Hugo Boss and Diesel did not immediately respond to requests for comment.

Human rights groups say more than one million Uighurs and other Muslim minorities have been interred in camps in China’s far-western Xinjiang, where they face abuses, including forced labour, forced sterilisation, beatings and rape.

Beijing has denied committing human rights abuses, including genocide, and argued that its “vocational education and training centres” have dramatically reduced violent extremism and poverty. (Al Jazeera)