(Bloomberg) -- The Justice Department is formally demanding information from the country’s four biggest meatpackers over potential antitrust violations, according to a person familiar with the matter, deepening scrutiny of an industry that’s been riled by shutdowns due to the coronavirus.

The department’s antitrust division sent civil investigative demands, which are akin to subpoenas, to the companies and is talking with state attorneys general about the probe after a group of states called for an investigation, said the person, who declined to be named because the inquiry is confidential.

Meatpacking is highly consolidated with four companies -- Tyson Foods Inc., JBS SA, Cargill Inc. and National Beef Inc. -- controlling about 80% of the U.S. beef processing market. Their dominance has sparked longstanding concerns about their pricing power over livestock suppliers. The companies didn’t immediately respond to requests for comment.

The Justice Department subpoenas to the meatpackers follow criminal indictments Wednesday of four executives of chicken processing companies, including the head of Pilgrim’s Pride Corp., America’s second-biggest chicken producer.

The U.S. is grappling with a meat crisis after the coronavirus pandemic sickened thousands of workers at slaughterhouses and forced plants to close. The producers have such a stranglehold on output that even a few closures create bottlenecks that ripple through the supply chain.

The disruptions have led to meat shortages and higher prices, even after President Donald Trump signed an executive order to keep plants running. With nowhere to send market-ready animals, hog farmers are set to euthanize millions of pigs, while cattle feeders are holding back animals or sending them into pastures.

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