One of the country’s largest private prisons are being sued under a class action suit that involve as many as 60,000 immigrants who have been detained.

According to a report by the Washington Post, thousands of immigrants detained in the US by the Immigration and Customs Enforcement (ICE), have been forced to work for a dollar a day, or sometimes for nothing at all. This act, the law suit claims, is a violation of federal anti-slavery laws.

The lawsuit is filed against GEO Group, a Florida-based corporation, that runs facilities to detain undocumented immigrants while they await their court dates.

“The Class action ruling by the US District Judge John Kane means that as many as 60,000 current and former detainees at the detention facility is Aurora (Colorado) are now part of the lawsuit without having to actively join as plaintiffs,” The Washington Post quoted Andre Free, a plaintiff attorney as saying.

The suit began with nine plaintiffs, detainees of ICE, who were forced to work without pay. The suit claims those who refused to work were threatened with solitary confinement.

According the Free, forced labor is a violation of the statute “Whether you’re calling it forced labor or slavery, the practical reality for the plaintiffs is much the same.” The plaintiffs were being required to work against their will under the threat of force.

The suit alleges GEO enriched itself by through cheap labor of detainees awaiting court dates.

Prison labor has two functions, to punish and to rehabilitate individuals who have been convicted of a crime. The detainees, however, have not been convicted but are awaiting a court’s decision on the immigration status.