Poultry and meat processor Tyson Foods (NYSE: TSN) reported fourth-quarter earnings results Monday, and also revealed that the Securities and Exchange Commission is investigating it over price-fixing allegations.

The commodity boom a few years back that only began easing last year caused the prices of beef to soar, which led consumers to turn to chicken as a cheaper alternative. Tyson and other poultry processors such as  Sanderson Farms (NASDAQ: SAFM) and Pilgrim's Pride (NASDAQ: PPC) have been accused of colluding to manipulate the supply of broiler chickens in the market beginning in 2008, resulting in prices rising higher than natural competition would have set them.

A class-action lawsuit was filed against a number of major chicken producers in September, alleging pricing collusion and anticompetitive behavior.

In a research report published in October, an industry analyst found the plaintiffs' claims extremely compelling, which sent Tyson's shares plunging. The company contends that report contains speculative conclusions and factual errors, and it says it plans on defending itself against the allegations made in the lawsuit.

In its quarterly filing, Tyson said it received a subpoena on Jan. 20, and said that while it is cooperating with the investigation, it remains in an "early stage."

In a Sanderson Farms filing last week, that company said it, as well as four other poultry producers that it doesn't name -- though one can presume the list includes Tyson -- were named in another class-action lawsuit filed on Jan. 27, alleging they "unlawfully conspired by sharing data on compensation paid to broiler farmers" to keep chicken prices below market rates. As is common, the suit is seeking triple damages, costs, and attorney fees. Pilgrim's Pride hasn't filed any notices with the SEC yet, though it should be reporting earnings soon.

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