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U.S. FBI conducting a probe into Herbalife-source

BOSTON, April 11 (Reuters) - The U.S. Federal Bureau of Investigation is probing Herbalife, the nutrition and weight loss company hedge fund manager William Ackman has called a pyramid scheme, a person familiar with the investigation said on Friday.

The news, first reported by the Financial Times, sent the company's stock price down nearly 14 percent.

The source said that the investigation has been going on for some time. Former Herbalife distributors have told Reuters that they had been contacted by agents who were interested in finding out more about the company's business practices.

(Reporting by Svea Herbst-Bayliss and Emily Flitter, editing by Richard Valdmanis)