“I am asking the DOJ to act expeditiously,” Trump posted Friday on social media. “Action must be taken immediately to protect Consumers, combat Illegal Monopolies, and ensure these Corporations are not criminally profiting at the expense of the American People.”

Shares for the world’s largest meatpacker, JBS NV, fell by as much as 6.2% on Trump’s comments, while Tyson Foods Inc. shares dropped by as much as 2% before paring losses to turn higher.

High cost of living dominated voter concerns this week in off-year elections, propelling Democrats to victory over Trump’s Republicans in races across the country. Polls showed voters gave Trump low ratings for his handling of the economy, and afterward his advisers vowed to place a greater focus on affordability. 

Beef has been Trump’s latest target for tamping down food inflation, as retail ground beef prices have surged to records. The US cattle herd has shrunk precipitously as ranchers have faced high interest rates and expensive feed and droughts. Rebuilding the herd will be a years-long process.

Still, Trump sought to place the blame on large corporation that process beef for consumers.

“While Cattle Prices have dropped substantially, the price of Boxed Beef has gone up — Therefore, you know that something is ‘fishy.’ We will get to the bottom of it very quickly. If there is criminality, those people responsible will pay a steep price!” Trump wrote in a subsequent post.

Read more: Trump Sparks Rare GOP Pushback With Purchases of Argentine Beef

The president’s handling of meat prices has drawn pushback from allies in agricultural states, who say his plan to quadruple the tariff-free quota on Argentine beef risks undercutting American farmers. 

Trump’s decision to impose a 50% tariffs on products from Brazil over diplomatic disputes also affected their beef exports. JBS and another meat giant, Minerva SA, are based there.