The largest beef processor in the world just keeps getting larger, prompting an Iowa congressman and senator to call for an investigation into possible anti-trust violations.

JBS SA, the world’s largest packer of beef and the third-largest beef processor in the United States, announced it plans to purchase National Beef Packing Co., Smithfield Beef Group and Five Rivers Ranch Cattle Feeding from Continental Grain Co. and Smithfield Foods.

Rep. Leonard Boswell, D-Iowa, and Sen. Chuck Grassley, R-Iowa, this week called on the Justice Department to conduct a thorough review of the proposed JBS acquisition.

Boswell serves as the chairman of the House Subcommittee on Livestock, Dairy and Poultry. He stated that current concentration in the beef-packing industry has made competition nearly nonexistent in certain parts of the country. “I’ve long been concerned about the concentration within the livestock industry,” said Boswell in a press release Thursday. “Should this acquisition go forward, I have concerns that this will limit options for small and independent producers.”

The acquisition could also increase meatpacker ownership of livestock, a subject that has long concerned Grassley. Proposed legislation he sponsored to ban packer ownership of livestock was passed in the Senate’s version of the new Farm Bill. Cattle-feeding operations that JBS is proposing to purchase would be “packer owned” and would be illegal if the bill becomes law.

“I have been pressing the Justice Department about consolidation in agriculture, but the department doesn’t appear to think there is a problem,” said Grassley in a press release. “Quite honestly I don’t know how much longer they can continue to let these mergers slide by. Now producers will only have three major beef packers to sell their livestock to. Is it going to take only one packer in the industry for the Justice Department to say there isn’t competition?”