FILE – This Nov. 18, 2011, file photo, shows a Tyson food product, in Montpelier, Vt. The Department of Justice tipped its hand last week when it requested a temporary halt to discovery proceedings in a 2016 class-action lawsuit filed by food distributor Maplevale Farms. Maplevale accuses Tyson Foods Inc., Perdue Farms Inc. and others of conspiring to fix poultry prices between 2008 and 2016. (AP Photo/Toby Talbot, File)

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CHICAGO (AP) — The U.S. government is investigating price-fixing charges against the country’s biggest poultry companies.

The Department of Justice tipped its hand last week when it requested a temporary halt to discovery proceedings in a 2016 class-action lawsuit filed by food service distributor Maplevale Farms.

Falconer, New York-based Maplevale Farms accuses Tyson Foods Inc., Perdue Farms Inc., Pilgrim’s Pride and others of conspiring to fix poultry prices between 2008 and 2016. The suit claims the companies shared information through a third-party data firm and restricted supply by destroying breeder hens on several occasions.

The government asked the U.S. District Court in Chicago for a six-month delay to protect an ongoing grand jury investigation. A federal judge is scheduled to rule on the request Thursday.

The case is one of nearly 40 filed by grocers, restaurants and others against the poultry companies. Kroger, Walmart, the Hooters chain and Darden Restaurants — which owns Olive Garden — are among those who have sued.

Tyson shares fell 1% to $80 in afternoon trading, while shares of Pilgrim’s Pride Corp. were down nearly 1% to $25.30.

The Justice Department has also been investigating price-fixing in the canned tuna fish industry. In October, StarKist announced it would plead guilty to fixing prices in the U.S. between 2011 and 2013.