The raid by U.S. Immigration and Customs Enforcement special agents at the Columbia Farms poultry processing plant in Greenville, S.C., was part of an ongoing, 10-month criminal investigation into its employment practices, the Justice Department said in a news release.

The investigation already resulted in criminal charges against 11 supervisors and a human resources manager.

"Today's enforcement operation is the latest step in a comprehensive criminal investigation focused on identifying the individuals involved in allowing unauthorized workers to gain employment," said Kenneth Smith, ICE special agent in charge in Atlanta. "By holding employers accountable, we are diminishing the magnet and discouraging others from breaking the law."

Assistant U.S. Attorney Kevin McDonald told WYFF-TV in Greenville that an examination of immigration paperwork for 825 workers at Columbia Farms showed more than 775 of them allegedly contained false information.