The stock began dropping Monday afternoon amid speculation that billionaire Carl Icahn was winding down his investment. It then began recovering in the last 15 minutes of the trading day and continued its rebound after hours.

Charles Gasparino, a reporter for Fox Business, helped lift the shares in extended trading when he wrote on Twitter that Icahn hasn’t sold his stake. After the stock dropped as much as 14 percent intraday to $38.63, it recovered to $40.21 at the close. The shares climbed as high as $43.33 in late trading.

Icahn is the highest-profile supporter of Herbalife, pitting him against fellow billionaire Bill Ackman, who has called the company a pyramid scheme. Herbalife’s other major shareholders include Soros Fund Management LLC, Richard Perry’s Perry Corp. and William Stiritz, according to data compiled by Bloomberg.

Icahn, whose firm owns an almost 19 percent stake, didn’t respond to a request for comment. Julian Cacchioli, a spokesman for Los Angeles-based Herbalife, declined to comment.

Ackman’s Campaign

After making an initial $1 billion bet against Herbalife, Ackman’s Pershing Square Capital Management LP is trying to profit from a drop in its share price. Ackman has spent $50 million on a two-year campaign to shut down the company.

Ackman claims that the business misleads distributors, misrepresents sales figures and sells a commodity product at inflated prices. The Federal Trade Commission and law enforcement have been investigating the allegations. Herbalife, which sells products in more than 90 countries through a network of independent distributors, has repeatedly denied Ackman’s assertions.

Icahn — who has a net worth of $23.6 billion, according to the Bloomberg Billionaires Index — has served as a counterbalance to Ackman. The billionaire disclosed a stake in Herbalife early last year and has become increasingly involved with the company. That includes naming five directors to the board.