Federal authorities say more than 300 workers at the Agriprocessors meat processing plant in Postville in northeast Iowa have been arrested for immigration violations. U.S. Immigration and Customs Enforcement agents entered the plant at ten this morning (Monday).

The U.S. Attorney for Iowa’s Northern District, Matt Dummermuth says coordination for the raid has been in place for some time. He says this is the largest such operation in the history of Iowa and the planning has been going on for months.

Dummermuth talks about the specifics of the search warrants issued today and says they were looking for evidence of aggravated identity theft, fraudulent use of Social Security numbers and other crimes, as well as a civil search warrant for people illegally in the United States. The investigation started last October.

Dummermuth says plant workers taken into custody will be held at a temporary detention hall at the National Cattle Congress fairgrounds in Waterloo. Women will be held at local county jails. Authorities are working with the Iowa Department of Human Services to provide caregiver services for children of detained family members. Agriprocessors is the nation’s largest kosher meatpacking facility.