MOUNT PLEASANT, Texas — Federal agents arrested hundreds of people yesterday in raids at Pilgrim’s Pride chicken plants in five states, the latest crackdown on illegal immigrant labor at the nation’s poultry producers.

In separate sweeps, authorities also arrested dozens of workers at a doughnut factory in Houston and the operators of a chain of Mexican restaurants in upstate New York. The arrests at Pittsburg, Texas-based Pilgrim’s Pride Corp., the nation’s largest chicken producer, included charges of identity theft, document fraud, and immigration violations. The company worked with Immigration and Customs Enforcement agents ahead of the raid, a company spokesman, Ray Atkinson, said. “We knew in advance and cooperated fully,” Mr. Atkinson said.

An assistant secretary for ICE, Julie Myers, confirmed the company is cooperating, though she said the raids grew out of an investigation that produced arrests last year at the company’s plant in Mount Pleasant.

No criminal or civil charges have been filed against Pilgrim’s Pride, which has about 55,000 employees and operates dozens of facilities mostly across the South and in Mexico and Puerto Rico, supplying the KFC restaurant chain and other customers. ICE said nearly 300 were arrested, but Pilgrim’s Pride officials said about 400 hourly, non-management employees were arrested.

“We have terminated all of the employees who were taken into custody and will terminate any employee who is found to have engaged in similar misconduct. We are investigating these allegations further,” Mr. Atkinson said.