Carl Icahn is telling other investors he has bought a stake in nutritional supplements seller Herbalife, according to a Dow Jones report on Wednesday.
Last week, the New York Post quoted sources as saying Icahn had taken a long position in the company.
With the reported stake, the billionaire investor is betting against Pershing Square's Bill Ackman, who announced a major short position in Herbalife last month.
Ackman, who has a 20 million share short position, has called Herbalife a pyramid scheme and has argued that federal regulators will eventually shut the company down.
Icahn is also lining up on the side of Third Point's Dan Loeb. The activist investor disclosed an 8 percent stake in Herbalife earlier this month.
In a letter to investors, Loeb, citing Herbalife's 32-year history, called Ackman's short thesis that the government was going to step in a shut the company down "preposterous."
In laying out his bullish case in an investor letter, Loeb said "the shares could be worth $55 to $68, offering 40 to 70 percent upside and making the company a compelling long investment for Third Point."