The builder of a downtown San Jose apartment tower shelled out $250,000 to workers to settle labor violations alleged by federal investigators. Full Power Properties LLC—the builder that succeeded KT Urban on the the 650-unit Silvery Towers project—owed the money to 22 workers, the U.S. Department of Labor (DOL) announced last week.

Investigators found that Full Power Properties profited off underpaid workers employed by Job Torres, a subcontractor doing business as Nobilis Construction. During off hours, those workers lived in captivity, in a squalid warehouse run by Torres.

Acting on a tip that Hayward-based Nobilis Construction used undocumented workers as slaves, agents from the U.S. Department of Homeland Security served search warrants at multiple sites in August of 2017, took Torres into federal custody and referred the case to the DOL‘s Wage and Hour Division.

Investigators say they found that Torres kept workers in a cramped second-story loft hidden behind a wall, with wood bunks and no running water. Torres allegedly locked the door from the outside, which led investigators to conclude that the workers were being held against their will.

According to the feds, Torres smuggled workers in from Mexico and would threaten them into submission by mentioning to anyone who complained that he knew people from drug cartels. The construction boss allegedly collected contact information for each worker’s family “in case of emergency,” so he knew where their loved ones lived.

There were signs of trouble long before federal investigators began looking into claims of forced labor in February of 2017. Silvery Towers developer KT Urban, which enjoyed tax breaks from the city to incentivize the project, came under fire in 2016 for hiring non-union workers, prompting a series of protests by local labor unions.

“The protesters warned the city that this is what happens when you go non-union—you end up with wage theft,” says Ruth Silver-Taube, attorney and legal services chair of the South Bay Coalition to End Human Trafficking. “Some of them even went to the city of San Jose and complained, ‘Why are you allowing these kinds of projects?’ And you know what? They were right.”

Silver-Taube, whose coalition advocated for the victims, called the Silvery Towers wage theft case one of the most egregious in recent memory. Authorities had to bring in medical vans to some construction sites because the workers were so badly injured.

“Some employers get so greedy, that not only do they not pay their workers, or underpay them, but they also keep them in conditions of involuntary servitude where they’re not free to leave,” she explained in a phone call Friday. “This case is emblematic of exactly that type of situation. It is pure greed.”

Wage and Hour Division District Director Susana Blanco said what happened to Torres should serve as an example to other contractors.

“The U.S. Department of Labor will do everything in its power to stop employers who violate the law from gaining an unfair competitive advantage over those who play by the rules,” she said in statement to reporters last week. “This case also represents a major victory in the fight against the scourge of human trafficking.”