US officials said workers entered on tourist visas and without proper visa authorisation. They were also forced to incur debt of thousands of dollars for airfare and recruitment fees before their employment in Saipan, according to the settlement.

“These settlements ensure that thousands of workers will receive the wages they legally earned, while simultaneously sending a strong, clear message to other employers,” said Bryan Jarrett, the department’s wage and hour acting administrator in a statement.

“Employers who evade the law in an attempt to reduce expenses must not gain a competitive advantage over those who play by the rules. Regardless of where work is performed in the US or its territories, we will continue to enforce the law and level the playing field.”

The Chinese labourers worked 13 hours a day without weekends or holidays and had their passports confiscated upon arrival in Saipan, said Li Qiang, executive director of New York-based China Labour Watch, an advocacy group. Li communicated with the affected workers and liaised with US officials to seek retribution for owed wages.

“More Chinese companies are expanding abroad and in regions like the US and Europe hiring labour there can be expensive,” Li said. “Firms will prefer bringing Chinese workers.”

But often, the workers are lured with false promises such as high wages and even help in obtaining a green card – none of which materialises once they arrive. Higher fines and penalties levied by US authorities would help combat these practices, Li said.

Hong Kong-based Imperial Pacific International contracted with the four Chinese firms for construction on Saipan. The company said it would release a statement regarding the settlement on Tuesday in Hong Kong.

Monday’s settlements are part of a wider investigation into the company’s casino and hotel project on the island.

Saipan island in the western Pacific is the seat of government of the Northern Mariana Islands.