The US Department of Justice (DOJ) has expanded its antitrust investigation into beef affordability to include eight large retailers, among them Walmart and Costco.

The wider probe also covers Ahold Delhaize USA, Albertsons, Aldi, Kroger, and Publix, according to a DOJ post on X.

The move follows an investigation opened in May into the “Big Four” meatpackers, namely JBS, Cargill, Tyson Foods and National Beef.

The DOJ has said those companies control more than 85% of the US beef processing market.

The department added that associate attorney general Stanley Woodward Jr sent letters to the eight retailers about “recent increases in the retail price for beef”.

“Beef prices are a critical concern to Americans, and a priority for this Justice Department,” the post on X read.

Letters seen by FOX Business set out the scope of the inquiry. They show federal antitrust officials are reviewing retailers’ beef pricing strategies, profit margins, costs and purchasing arrangements going back to 2020.

“The Antitrust Division is assessing trends in beef prices - a matter of critical concern to the American public, and a priority for the United States Department of Justice,” Woodward wrote in identical letters dated 14 July and sent separately to each company.

The DOJ said it will seek records linked to retail beef sales and prices, wholesale purchases, costs and margins, and pricing and purchasing strategies.

It is also requesting companies’ analyses of trends in wholesale and retail beef prices.

Investigators are also seeking information on other elements affecting beef prices.

The department has also asked company personnel to brief investigators on four areas.

In addition, the DOJ asked company staff to brief investigators on four areas, including shifts in beef pricing strategies and margins between 2020 and 2026, cost changes over the same period, and wholesale purchasing arrangements with meatpackers.