Herbalife shares are ripping

Shares of nutritional supplements seller Herbalife were surging on Friday following a report that the FBI is probing whether Bill Ackman and his contractors manipulated the company's stock.

The stock was last trading up $2.19, or 6.59%, at $35.44 per share.

Herbalife is the company that Ackman, the CEO of Pershing Square, is infamously short.

For more than two years, Ackman has been on a very public crusade against Herbalife-a multi-level marketer he believes is operating as a "pyramid scheme" that targets poor people. It's his contention that regulators, specifically the Federal Trade Commission, will shut the company down. The FTC opened an investigation into Herbalife in March 2014.

Herbalife has denied and continues to deny Ackman's allegations.

Ackman told CNBC on Friday morning that neither he nor his fund has been contacted by the FBI.

Here's a 5-day chart of the stock: