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 distributor Maplevale Farms.

Maplevale accuses Tyson Foods Inc., Perdue Farms Inc. and others of conspiring to fix poultry prices between 2008 and 2016. The suit claims the companies shared information and restricted supply by destroying breeder hens.

The government said it wants a six-month delay to protect an ongoing grand jury investigation. A federal court judge in Chicago 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 and Walmart are among those who have sued.