Federal immigration officials believe the five companies owning poultry-processing plants raided last week in Mississippi knew they were illegally hiring undocumented immigrants, according to the Washington Post.

According to recently released search warrant affidavits, the Post reported Thursday, a Homeland Security agent “said there is probable cause to believe that the chicken plants in Mississippi intentionally hired undocumented workers who presented fraudulent documents.”

“The companies for years have employed a stream of Guatemalan and Mexican immigrants who are not authorized to work in the United States, according to the search warrant affidavits,” the Post says.

“Immigration and Customs Enforcement [ICE] carried out the raids at seven chicken-processing plants operated by the companies, arresting 680 workers, about half of whom have been released to await further hearings.”

ICE spokesman Bryan Cox told the Post no charges have yet been filed against either the workers or their employers since the raids.

The affidavits say that “individuals or companies shown to have ‘actual knowledge’ of violating the employment law — meaning they knowingly hired at least 10 people not authorized to work for a year-long period — can be fined as much as $3,000 per undocumented worker and imprisoned for as much as six months,” the Post says.

The five companies in question are: Koch Foods, Peco Foods, PH Food, A&B and Pearl River Foods.

“An undocumented Mexican woman working in a Peco Foods plant in Bay Springs, Miss., told immigration officials that she had come to the state because people in Mexico had told her that jobs were available at the chicken plants there,” the Post says.