NEW YORK (NYTIMES) - For the past six years, federal prosecutors said, two former Chinese diplomats living in the New York area brought numerous construction workers to the United States from China on diplomatic visas, ostensibly to do repairs on Chinese government buildings.

But according to an indictment unsealed Thursday (Dec 8), the workers were also forced to work private projects and were threatened with the loss of their homes in China if they refused to do so.

The indictment, in US District Court in Brooklyn, accused the former diplomats, Zhong Dan, who served at the Chinese Consulate in New York from 2001-06, and Wang Landong, who worked at the Chinese Embassy in Washington from 2001-07, of bringing the workers from China on so-called A2 or G2 visas.

While the workers did work at diplomatic missions, court papers say they were forced into "debt bondage contracts" and made to work on several outside projects, including at least two private homes, in Queens and on Long Island.

Under one of these contracts, from July 2012, Zhong, 47, and Wang, 49, agreed to pay a worker a base salary of about US$1,180 a month but required a cash deposit of about US$22,000, court papers said.

The deposit was to be kept, according to a criminal complaint, and the worker could be sent back to China if he broke the contract's provisions. Those provisions required the laborers not to criticise their employers, meet secretly with anyone, try to escape or even leave their living quarters.

At an arraignment Thursday, Zhong, who lives in Livingston, New Jersey, pleaded not guilty to the charges. His lawyer, Nick Ackerman, told Judge Dora L. Irizarry that the contracts did not seek to punish the workers for escaping and that prosecutors had mistranslated the contract language.

According to federal prosecutors, Wang, who has returned to China, would seize the workers' passports when they entered the United States to keep them from fleeing.

The workers were often housed, several together, in rundown homes, court papers said. In 2011, for example, authorities in Jersey City shut down a single-family rowhouse on Pavonia Avenue that court papers said was connected to the forced-labor scheme after inspectors discovered 28 Asian men living there.

The house had homemade electrical wiring and doors that locked from the outside, court papers said.

In June 2015, agents with the FBI found a group of the workers doing renovations at a house in Old Brookville, New York, in Nassau County. According to court papers, the agents later found a "proposal" for the project in which Wang had written: "No filing with the local department of buildings, No permits, No insurance or bond, No licenced plumbing and electrical trades will be used."

A few months later, other federal agents found another group of workers performing renovations on the first floor of a house in Fresh Meadows, Queens. According to court papers, when the agents asked Wang about the project, he said it had been undertaken out of "friendship" for an acquaintance and done at "no charge."

The court papers do not explain how the two defendants were able to obtain diplomatic visas for the workers, though a prosecutor said in court that their construction business had an office at the Chinese mission to the United Nations.