The chicken-processing company whose facilities were raided Tuesday by Immigration and Customs Enforcement agents said it is cooperating with the investigations and resuming operations.

More than 160 suspected illegal aliens were arrested at Koch Foods' chicken packaging plant in Fairfield, and its corporate headquarters in Park Ridge, Ill., also was raided. Those who have been arrested face deportation proceedings.

The Hamilton Journal-News reported that the company's hiring practices have been under investigation for more than two years.

Koch said in a statement on its Web site that it is "fully cooperating" with immigration authorities, and that it requires all employees to provide documentation of legal residency. It also said it have established a program to audit documentation, and is implementing another through the Department of Homeland Security to verify workers' legal status.

The company also said in the statement that it is continuing normal business operations at its Park Ridge site, and resumed operations at the Fairfield plant Tuesday evening.

Koch Foods is one of the largest poultry processors in the United States, operating its own hatcheries and feed mills, as well as processing and packaging plants. Koch ranks 274th on Forbes magazine's list of the country's largest privately owned companies.