SACRAMENTO, Calif. (AP/CBS13) — A Shasta County couple was sentenced Monday to several years each in federal prison for conspiring to force a Guatemalan relative and her two daughters to perform long hours of physically demanding work every day of the week for little or no pay.

Nery Martinez Vasquez was sentenced to 6 1/2 years in prison and Maura Martinez to three years in prison after pleading guilty in August. They were each fined $25,000 and ordered to pay $300,000 in restitution.

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The couple, both 54 and from Shasta Lake which is just north of Redding, are naturalized U.S. citizens originally from Guatemala.

Federal prosecutors said they promised their relative a “better life” if she came to America in September 2016 with her two daughters, then ages 15 and 8.

But they then forced the three to overstay their visas and work at their restaurant, called Latino’s, and at their Redding Carpet Cleaning & Janitorial Services, which served area businesses including multiple car dealerships.

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They threatened to have their relatives arrested for overstaying their visas and told the daughters they couldn’t go to school because they would be deported, prosecutors said.

They said Martinez Vasquez beat the daughters with a stick that had the children’s names and nicknames written on it along with the phrase “what goes up, must come down.”

“Forced labor, a form of human trafficking, is … difficult to identify and investigate without cooperation of fearful victims who believe escape is not an option because of the lies they have been told by their exploiters,” Sean Ragan, special agent in charge of the FBI’s Sacramento Field Division, said in a statement. “This case highlights how such crimes may occur in public view at a legitimate business yet go unnoticed.”

Under a plea agreement, prosecutors dropped charges alleging that in 1997 the couple conspired to kidnap a 13-year-old girl from her Las Vegas home, then held her against her will for nearly two years while Martinez Vasquez repeatedly raped and sexually molested the girl.

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“These defendants exploited vulnerable victims, forcing them to work in their businesses, failing to pay wages, and depriving them of basic human rights,” said U.S. Attorney Phillip A. Talbert, of the Department of Justice Eastern District of California. “Now they have been sentenced to years in prison and have paid hundreds of thousands of dollars in restitution to their victims.”