The U.S. Justice Department has opened a criminal investigation into allegations that chicken processors, including Tyson Foods Inc., Pilgrimís Pride Corp. and Sanderson Farms Inc., conspired to fix prices.

Prosecutors disclosed the grand jury probe in a court filing Friday in Chicago, where civil lawsuits against more than a dozen companies in the industry are pending. Tyson, Pilgrimís and Sanderson alone control almost half of the U.S. chicken market.