NEW YORK (Reuters) — A hedge-fund manager referred to as "Tipper X" in the Galleon Group insider-trading case could lead prosecutors to widen the probe to hedge funds that had not been previously implicated, the Wall Street Journal claimed, citing people familiar with the case.

"Tipper X" was identified as Thomas Hardin, a former trader at Lanexa Global Management, the newspaper said, citing people familiar with the investigation.

The New York Times separately identified the 32-year-old Hardin as "Tipper X".

A call to what is believed to be Hardin's home was not immediately returned. Hardin's lawyer could not immediately be located.

Hardin's name is included on a list of potential witnesses that the US Securities and Exchange Commission provided to defence lawyers in the civil Galleon insider-trading case.

A person familiar with the list confirmed that Hardin's name is on the list but could not confirm that the hedge fund trader is the mysterious Tipper X.

The source also said the SEC has been circulating list of potential witnesses for several weeks and Hardin's name has been known by defence lawyers for a while.

A large number of cooperating witnesses could spawn other investigations, the Journal said, citing people close to the situation.

In addition to Hardin, Ian Murray, a New York hedge fund manager who has not been charged with wrongdoing, and Gustavo D'Souza, whose connection to the case is unclear, appear on the list of potential government witnesses, the Times said.

Neither could immediately be reached for a comment.

Tipper X was allegedly tipped off to a pending Blackstone Group Inc takeover of Hilton Hotels Corp July 2, 2007, according to an SEC complaint.

The complaint says Tipper X then passed the information on to Gautham Shankar, a trader who has admitted to trading on inside information.

Twenty-one people have criminally or civilly been charged in the Galleon insider trading case that involves employees of some of America's best-known companies.

Galleon Group hedge-fund founder Raj Rajaratnam, has also been chared for allegedly participating in insider-trading rings. Rajaratnam has denied wrongdoing.

Those cases stem from the SEC's increased cooperation with federal prosecutors.

On Tuesday, a federal judge let stand the $100 million bail set for Galleon founder Raj Rajaratnam, the central figure in the probe.