It was unclear how many more would be detained on immigration charges at the plants in Texas, Arkansas, Florida, Tennessee and West Virginia, she said. Agency spokeswoman Kelly Nantel had estimated at least 100 such administrative arrests.
Ray Atkinson, a spokesman for Pittsburg-based Pilgrim's Pride, did not immediately return calls for comment.
Those facing criminal charges will be detained by U.S. marshals, Nantel said. ICE agents will interview others to decide whether they would be detained or released pending immigration hearings.
In Arkansas, federal agents raided a north Arkansas poultry plant over suspected immigration violations, authorities said.
Temple Black, a spokesman for U.S. Immigration and Customs Enforcement, said the arrests were part of an ongoing criminal investigation that involved a poultry plant in Batesville, Ark. Black declined to say how many people were arrested or describe the nature of the investigation.
The other plants involved were in Mount Pleasant, Texas; Live Oak, Fla.; Moorefield, W.Va.; and Chattanooga, Tenn.
Myers said the raids were part of a long-term investigation into practices at Pilgrim's Pride, the nation's largest chicken producer.
In January, 24 people, including some former employees, were indicted as part of the probe after investigators said they were involved in an identity theft ring to help get jobs for illegal immigrants at plants in Pittsburg and Mount Pleasant.
Pilgrim's Pride has about 55,000 employees and operates dozens of facilities mostly across the South and in Mexico and Puerto Rico.