French prosecutors have launched an inquiry into four fashion retailers suspected of concealing crimes against humanity in China’s Xinjiang region, a judicial source said on Thursday.

The procedure is linked to accusations against China over its treatment of minority Muslim Uighurs in the region, including the use of forced labour, the source said.

The source told Reuters Uniqlo France, a unit of Japan’s Fast Retailing, Zara owner Inditex, France’s SMCP and Skechers were the subject of the investigation, confirming a report by French media website Mediapart.

“An investigation has been opened by the crimes against humanity section of the anti-terrorism prosecution following the filing of a complaint,” the source said.

Inditex said it rejected the claims in the legal complaint, that it conducted rigorous traceability controls and would fully cooperate with the French investigation.

“At Inditex, we have zero tolerance for all forms of forced labour and have established policies and procedures to ensure this practice does not take place in our supply chain,” the company said in a statement.

SMCP and Uniqlo France were not immediately available to comment outside of European business hours. Skechers did not immediately respond to a request for comment.

Two non-governmental organisations (NGOs) filed a complaint in France in early April against multinationals for concealment of forced labour and crimes against humanity.

Several Western brands including H&M, Burberry and Nike have been hit by consumer boycotts in China after raising concerns about forced labour in Xinjiang.

The United States in late March highlighted a deteriorating picture for human rights across the world, calling out China’s repression of Uighurs.

By Benoit Van Overstraeten, Richard Lough and Jesus Aguado