A grand jury has been convened in the Ackman Herbalife stock-manipulation investigation

Bill ackmanREUTERS/Eduardo MunozWilliam Ackman, founder and CEO of hedge fund Pershing Square Capital Management

The federal probe into alleged market manipulation of Herbalife stock by Bill Ackman took a dramatic turn on Tuesday with a report that at least one person has been subpoenaed to appear before a federal grand jury, indicating that the investigation may lead to criminal charges.

Investigators working for the FBI and Manhattan U.S. Attorney’s office have interviewed lobbyists at Global Strategy Group, a politically-connected firm hired by Ackman to push his case that Herbalife is a pyramid scheme, reports the Hartford Courant.

At least one person — a hair stylist from Hartford apparently tied to a letter-writing campaign intended to discredit Herbalife — was subpoenaed late last month to appear before a federal grand jury in New York, according to sources cited by the Courant.

Ackman, the founder and CEO of Pershing Square Capital Management, publicly stated back in 2012 that he is shorting shares of the company, a bet that could net him over $US1 billion. He said last week that he has spent $US50 million on lawyers and lobbyists to convince federal and state regulators to investigate his complaints and to promote his “very firmly held view that Herbalife is a pyramid scheme,” reports the Courant.

During a CNBC interview in January this year, Ackman declared that he’s doing “God’s work” on Herbalife.

NOW WATCH: A lawyer in Florida has come up with an ingenious way for drivers to evade drunken-driving checkpoints

Business Insider Emails & Alerts

Site highlights each day to your inbox.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.