Labor authorities in the United States have ordered contractors in the Commonwealth of the Northern Mariana Islands to pony up a total of $13.9 million in back wages and damages to 2,400 workers who came from China to build the Imperial Pacific Resort.

On Monday, the U.S. Department of Labor (USDOL) announced that four China-based construction contractors—MCC International Saipan Ltd. Co., Beilida New Materials System Engineering Co. Ltd., Gold Mantis Construction Decoration, and Sino Great Wall International Engineering Co. LLC—were found to have paid its workforce “less than the minimum wage and overtime pay” required by the U.S. Fair Labor Standards Act (FLSA).

Investigators with the department’s Wage and Hour Division said the Chinese workers contracted by MCC, Beilida, and Gold Mantis were brought to Saipan under the tourist visa waiver program, noting that these “tourists” worked on the casino development site without the proper work visas.

The employees had to pay for their own airfare and recruitment fees, resulting in at least $6,000 of debt, according to the U.S. labor department officials.