U.S. Immigration and Customs Enforcement agents swept through seven work sites in six cities across Mississippi on Wednesday, arresting approximately 680 people the agency said were undocumented immigrants in what officials said is the largest single-state workplace enforcement action in U.S. history.

The raids targeted agricultural processing plants, part of a year-long investigation into illegal employment of immigrants in the state, officials said. They did not say how many individuals they were targeting in the operations, nor what proportion of those taken into custody were what ICE calls “collateral” arrests — those who were swept up along with those ICE was seeking.

ICE acting director Matthew Albence said at a news conference in Jackson, Miss., that some of those arrested will be prosecuted for crimes, others will be swiftly deported, and some will be released pending immigration court hearings. Albence said the raids were part of normal ICE operations that seek to enforce U.S. immigration laws.