SAN FRANCISCO (AP) — At least a dozen immigrant workers who were forced to live in squalid conditions and to work construction jobs for little or no pay were rescued from a forced labor ring in California allegedly run by a man who has been arrested, federal and local officials said Wednesday.

Many of the immigrants who were in the country illegally lived in a warehouse in the San Francisco Bay Area city of Hayward that did not have running water and was locked from the outside at night, the office of U.S. Attorney Brian Stretch said in a statement.

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The immigrants, identified in court documents only by their initials, worked at construction projects and received no pay or were paid less than minimum wage, officials said. Investigators declined to release more information about the workers, such as what countries they came from or how long they have been in the United States.

At least seven people were freed from the warehouse Wednesday, federal prosecutors said.

Job Torres Hernandez, 37, of Hayward was indicted last week on charges that he harbored immigrants living in the country illegally for commercial advantage. Hernandez was arrested Tuesday. His court file did not list an attorney, and one was expected to be appointed Wednesday during a plea hearing in federal court in Oakland.

Hernandez had at least five people concealed on his property since July 2015, according to a federal court indictment unsealed Wednesday. It accused him of knowingly harboring the illegal workers for his own financial gain.

Victim support personnel were available to offer help and to connect the rescued workers to nonprofit service organizations, Hayward Police Chief Mark Koller said.

“Otherwise, the workers who were rescued were free to go,” Koller said in a statement.

Immigration and Customs Enforcement agents carried out the search and arrest warrants at several locations in Hayward as part of an ongoing investigation into forced labor and human trafficking, he said.

If convicted, Torres faces up to 10 years in prison and a $250,000 fine.