Federal agents are planning to conduct a major worksite enforcement operation at a national food service chain in the coming weeks, according to an internal Immigration and Customs Enforcement (ICE) document reviewed by The Daily Beast.

The current plan is focused on employers who exploit undocumented workers by illegally paying them below the minimum wage. The operation will target locations around the country and will likely result in charges of “harboring illegal aliens,” according to an ICE official.

“These people are basically being used as slave labor,” said the official, who spoke to The Daily Beast anonymously because he was not permitted to discuss impending operations on the record.

The plans detailed in the document are the strongest indication to date that Immigration and Customs Enforcement officials are increasing what’s called “worksite enforcement”—meaning, efforts to prosecute people who employ undocumented immigrants. As with all complex law enforcement operations, there’s a chance this one is altered or even scuttled. If it does go according to plan, however, it will be the first major worksite enforcement action of an administration that has promised to prioritize this core ICE mission.

The food service industry is a particularly ripe target, with The Migration Policy Institute estimating that about 9 percent of food service workers in the U.S. are undocumented.

According to the plans, the operation will focus on franchise owners who exploit undocumented workers. The agency has already done preliminary investigations and picked targets, The Daily Beast has learned.

ICE is divided into two components: Enforcement and Removal Operations (ERO), which arrests and detains undocumented immigrants, and Homeland Security Investigations (HSI), which investigates crimes related to customs and migration. HSI agents handle a host of issues, including art forgery, child exploitation, and drug crop eradication. They will also be helming this coming operation.

The operation will build on previous work.

On April 27, 2015, Farrukh Baig—who owned and operated 14 7-Eleven stores—pleaded guilty to wire fraud and to “concealing and harboring illegal aliens,” according to the Justice Department. According to court documents, Baig and several co-conspirators hired more than 100 undocumented immigrants to work in his stores. He then used the stolen identities of Americans to conceal his workers’ identities. Because the workers were undocumented, Baig and his store managers stole much of their wages and then paid them in cash, below the minimum wage.

Baig and his managers housed the undocumented immigrants at homes near the 7-Eleven stores where they worked, and deducted rent from their paychecks. In all, their scheme lasted more than 13 years. Federal prosecutors said that over the course of two of those years, they stole more than $1.25 million from the undocumented immigrants working for them.

Undocumented workers are uniquely vulnerable to this kind of exploitation because many fear that talking to law enforcement will lead to their deportation.

The ICE official who spoke to The Daily Beast said undocumented workers who cooperate with the agency could potentially be eligible for U visas, which let victims of crimes who testify against their perpetrators stay in the United States temporarily.

Tom Homan, the acting director of ICE, said in a speech last month at the conservative Heritage Foundation that the agency would target more work sites in the coming months. He also said the agency would target undocumented workers as well as their employers.

“Not only are we going to prosecute the employers that hire illegal workers, we’re going to detain and remove the illegal alien workers,” he said.

“When we find you at a work site, we’re no longer going to turn our heads,” Homan said after the event, according to CNN. “We’ll go after the employer who knowingly hires an illegal alien... but we’re always going to arrest a person who is here illegally. That is our job.”