Gary Strauss

USA TODAY

Herbalife shares sank as much as 15% in Wednesday trading after the nutritional supplements marketer said it is under Federal Trade Commission investigation.

Shares were up $2.91 (4.5%) to $68.30 before trading was halted at about 1:15 p.m. Trading reopened about 30 minutes later, and shares plummeted below $55. By day's end, Herbalife rebounded, closing down 7.4% to $60.57.

The trading halt and stock gyrations came after Herbalife said it had received a "civil investigative demand" from the FTC, but declined to elaborate.

"Herbalife welcomes the inquiry given the tremendous amount of misinformation in the marketplace, and will cooperate fully with the FTC,'' the company said in a statement. "We are confident that Herbalife is in compliance with all applicable laws and regulations."

The company's business plan has been criticized for months by Pershing Square hedge fund investor Bill Ackman, who made a $1 billion bet on the stock's collapse in December 2012 and had lobbied regulators and members of Congress to investigate the company's business practices.

In a Tuesday webcast, Ackman repeatedly called Herbalife's multilevel marketing and sales practice a pyramid scheme and charged that the company was violating Chinese labor laws. Herbalife denied Ackman's accusations in a statement Tuesday.

Ackman's efforts to bash Herbalife have drawn criticism and protracted exchanges from activist investor Carl Icahn, who aligned himself with management and amassed a 13% stake in the company last year. Icahn has said Herbalife is undervalued.

Herbalife had 2013 sales of $4.8 billion, up from about $4.1 billion in 2012. It markets energy and fitness snacks, drinks, vitamin supplements and skin-care products through 3 million distributors in more than 90 countries.

Among other personal care marketers with similar sales and distribution channels, USANA Health Sciences lost $3.10 (4.3%) to $69.82, while NuSkin Enterprises gained $4.78 (6.5%) to $77.89.

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