MEXICO CITY (REUTERS) - The US government on Wednesday (July 1) said it blocked an US$800,000 (S$1.1 million) shipment of hair extensions and accessories from China on suspicions that the products were made with forced labour.

The goods were held under a June order against a Xinjiang-based company suspected of using prison labour and forced labour with excessive overtime, withheld wages and restrictions on workers' movements, the Customs and Border Protection (CBP) agency said.

The United States bans the import of goods made entirely or in part by forced labour, whether prison work or bonded or forced child labour.

The CBP order dated June 17 called for the detention of goods made by Xinjiang's Lop County Meixin Hair Product Co.

The importers of the detained shipments must prove the merchandise was not produced with forced labour or export it elsewhere, the agency said.

"The use of forced labour is not just a serious human rights issue, but also brings about unfair competition in our global supply chains," said Ms Brenda Smith, executive assistant commissioner of the CBP's Office of Trade, in a statement accompanying the June order.

The autonomous Xinjiang region in north-west China is home to a large population of Muslim Uighur people, an ethnic minority who speak a Turkic language and face repression from the Chinese government.

The United Nations has said it has credible reports that 1 million Muslims have been detained in camps in the region.

China denies mistreatment of the Uighurs and says the camps are vocational training centres needed to fight extremism.

A spokesman for the Chinese embassy in the US said in an e-mail that the suspicions of forced labour were an effort to bring down Chinese business.

"The lawful labour rights and interests of the Chinese citizens of all ethnic groups, including those in Xinjiang, are protected by law," the spokesman said.

"The accusation of 'forced labour' in Xinjiang is both false and malicious."

The CBP has been criticised for not enforcing US law against forced labour imports enough, and critics say the agency's forced labour division is understaffed and underfunded.

A CBP spokesman told the Thomson Reuters Foundation that the agency has been working to develop and expand the division, and that the number of forced labour investigations was rising.

In October, the CBP said it had blocked imports suspected to have been made with forced labour from five countries, including clothing from China and diamonds from Zimbabwe.

The number of forced labour prosecutions is low, so the CBP's orders to halt imports are a powerful tool, said Ms Martina Vandenberg, head of the Washington-based Human Trafficking Legal Centre.

"Criminal justice remedies have failed," she said."Advocates are looking for more innovative and creative tools to combat forced labour in supply chains."

There were just 939 labour trafficking prosecutions around the world in 2019, according to the US State Department's most recent Trafficking in Persons Report.

The CBP can issue a "withhold release order" when it believes goods were made by forced labour, and it has issued 16 of them since March 2016.

The CBP said the blocked imports from Xinjiang, which included long hair extensions, weighed 13 tonnes and were held at a port in Newark, New Jersey.

Lop County Meixin also could not be reached for comment.

Two weeks ago, President Donald Trump signed legislation calling for sanctions on China over its treatment of Uighurs.

The State Department separately on Wednesday issued an advisory to caution businesses about supply chain links to Xinjiang.

In Britain, lawyers and campaigners are trying to halt imports of cotton goods originating from Xinjiang.