Bill Ackman Might Be Under Investigation...And It's Boosting Herbalife Stock

Update: At 6:56pm, Herbalife issued a response to reports "that individuals involved in the campaign orchestrated by Bill Ackman are under criminal investigation." The full statement can be seen here.

Herbalife Ltd. (NYSE: HLF) gained more than 6 percent in extended trading Thursday on a report that hedge fund manager Bill Ackman is under investigation for potential stock manipulation.

Ackman has been on a high-profile short-selling campaign against the multilevel marketer Herbalife since 2012, and has called the company a pyramid scheme.

The federal investigation is focused on whether false statements about Herbalife's business model were made to regulators by lobbyists hired by Ackman, according to a report late Thursday in The Wall Street Journal.

U.S. prosecutors based in New York, as well as the Federal Bureau of Investigation, have conducted interviews related to the probe in recent months, the report stated.

Neither Ackman nor his Pershing Square hedge fund has been served with a subpoena or been visited by FBI agents, according to the report, which noted that it's possible no charges will be filed.

Pershing Square told the Journal that it has "been completely transparent" in its Herbalife campaign and acted lawfully.

The Federal Trade Commission and the Securities and Exchange Commission have ongoing investigations into Herbalife, based at least in part on Ackman's allegations.