OKLAHOMA CITY (AP) — Owners of an Oklahoma hotel and other businesses engaged in a human trafficking scheme that lured workers from the Philippines promising good wages but instead paid them less than the minimum wage, according to a lawsuit.

Three Filipino workers brought to Clinton, Oklahoma, about 80 miles (128 kilometers) west of Oklahoma City, paid thousands of dollars in recruiting fees to cover visa-related costs that should be incurred by sponsoring U.S. employers, according to the complaint filed Wednesday in federal court. The lawsuit, filed by the American Civil Liberties Union and other groups, says the immigrants were threatened with physical harm when they complained that their compensation didn't meet contractual obligations. It also seeks class-action status.

Walter and Carolyn Schumacher, a married couple who own a Holiday Inn Express, steakhouse and waterpark in Clinton where the plaintiffs say they worked, didn't reply to calls on Thursday seeking comment. It wasn't known if they have a lawyer.

An FBI spokeswoman and an Immigration and Customs Enforcement spokesman said they were not aware of the case, but would not be able to comment on whether or not an investigation is underway. A U.S. Department of Labor spokesman said he was not aware of an investigation into the case.

Nonprofit law firm the Equal Justice Center and employee rights group Legal Aid at Work joined the ACLU of Oklahoma in filing the lawsuit. It seeks an unspecified amount in punitive and compensatory damages for the workers because it alleges they were paid less than their contract allows and less than the federal minimum wage.

The lawsuit contends that from 2008-14, the Schumachers' companies applied to the federal Department of Labor to employ more than 100 foreign workers.

It alleges that workers recruited for housekeeping jobs at the hotel were paid $4.25 per room cleaned. Servers at the steakhouse made $2 per hour plus tips, and housekeepers and servers at the waterpark made $1 to $2 per hour less than promised. Low pay and short workweeks meant the immigrants couldn't repay debts they incurred just to get to the U.S., the suit says.

The suit says Walter Schumacher intimidated employees by saying he was carrying a gun when he picked them up from the airport. The filing also claims that although the Schumachers promised they would pay for roundtrip airfare to and from the Philippines, Walter Schumacher said the only way he would send anyone back was "in a box."

Brady Henderson, an ACLU lawyer, said the public often thinks of human trafficking in the form of sex work.

"It has a lot more elements of indentured servitude or slavery than they realize," Henderson said. "Most people probably don't realize how prevalent it is, potentially in their own communities."

U.S. Secretary of State Rex Tillerson said in June there are 20 million victims of human trafficking around the world.