NEW YORK (REUTERS) - The owners and managers of more than a dozen 7-Eleven Inc stores were accused on Monday of hiring and victimising dozens of illegal immigrants, forcing them to live in substandard housing, giving them stolen identities and stealing their wages.

Federal authorities moved to forfeit the franchise rights to 14 of the convenience stores and seize five houses in New York worth more than US$1.3 million (S$1.63 million), making the case the largest criminal immigration forfeiture in Department of Homeland Security history, according to federal and state officials.

The eight men and one woman charged in the scheme ran 7-Elevens in New York and Virginia, according to two indictments unsealed on Monday.

"These defendants ruthlessly exploited their immigrant employees, stealing their wages and requiring them to live in unregulated boarding houses, in effect creating a modern day plantation system," said Ms Loretta Lynch, United States (US) Attorney for the Eastern District of New York, in a statement released with Homeland Security and the Social Security Administration as well as state and local police.

More than 50 illegal immigrants were overworked and cheated out of their wages, the authorities said. Because they were illegally in the country, the victims may have been afraid to report possible wrongdoing, they added.

The immigrants were given identities stolen from more than 25 people, including dead people and children, they said. The scheme was concealed from 7-Eleven headquarters, they said.

In a separate statement, 7-Eleven, which is owned by Seven & I Holdings Co Ltd of Japan, said it was cooperating with the investigation and would have no further comment for now.

The scheme generated millions of dollars in profits, said Mr Joseph D'Amico, Superintendent of the New York State Police which also worked on the case.

The victims were made to live in housing owned by the accused, leaving them "completely beholden" to their employers, he added.

The case may spread beyond Virginia and New York, as federal agents on Monday executed search warrants at about 30 other 7-Elevens around the country, and the investigation is ongoing, authorities said.

The nine defendants were charged with conspiring to commit wire fraud, stealing identities and concealing and harboring illegal immigrants.

If convicted, they could face 20 years apiece in prison on wire fraud conspiracy and alien harbouring charges. The multiple counts of aggravated identity theft carry mandatory, consecutive two-year prison terms.

The accused included a married couple, Farrukh and Bushra Baig, who owned or controlled twelve 7-Elevens, as well as Baig's brothers Zahid Baig and Shannawaz Baig and five other people.