Two US lawmakers have sent letters to the country's top egg companies seeking answers for why egg prices have ballooned to record highs in recent months, according to copies of the letters seen by Reuters.

The price of eggs was up 150% in January from a year prior to $4.80 a dozen, according to the Bureau of Labor Statistics, raising concerns among farmers and antitrust advocates who have warned about the power of top agriculture firms to set prices.

"American families working to put food on the table deserve to know whether the increased prices they are paying for eggs represent a legitimate response to reduced supply or out-of-control corporate greed," wrote Senator Elizabeth Warren of Massachusetts and Representative Katie Porter of California.

The letters were sent Thursday morning to the CEOs of Cal-Maine Foods, Hillandale Farms, Rose Acre Farms, Daybreak Foods, and Versova Management.

The US Department of Agriculture has pointed to record cases of avian influenza, which has killed more than 58 million chickens and turkeys since the beginning of 2022, as a reason for high prices. But a farm group recently asked federal regulators to investigate whether egg companies were price gouging.

The lawmakers said the spike in prices raises concerns about anti-competitive conduct and requested information on executive compensation, profit margins, avian flu impacts, and whether companies have communicated with one another about egg prices.

Only Cal-Maine Foods, which controls about 20% of the US egg market, is public. The company reported gross profits up 600% in a late-December filing with the Securities and Exchange Commission.

Cal-Maine, Daybreak, Hillandale, Rose Acre, and Versova did not immediately respond to requests for comment.

The lawmakers requested responses by March 1.