American sprinter Michael Johnson, one of the United States' most successful athletes, could lose his Sydney 2000 Olympics [Images] 4x400m gold medal after a former relay team mate admitted to doping.

Antonio Pettigrew, a member of the Sydney Games gold-winning relay team that also included Johnson and twins Alvin and Calvin Harrison, told a San Fransciso court on Thursday he had used banned substances after the 1996 Olympic trials.

• Marion Jones: Glory gone

Last year, the International Olympic Committee stripped the team mates of disgraced sprinter Marion Jones [Images] of their Sydney Games relay medals after she had similarly admitted to doping.

Pettigrew was testifying in a trial linked to the now-defunct San Franscisco-based Balco lab that provided banned substances to several prominent athletes, including Jones.

"Since the Balco story first broke, the IOC has been very keen to ensure that the impact it has had on the Olympic Games be thoroughly addressed and rectified through our disciplinary procedures," the IOC said in a statement.

"Recent revelations should be viewed with this in mind.

"All new elements coming out on the Balco case - be that from the hearings in the US this week or from other sources - will be studied by the IOC as part of its on-going and now long-standing look at this sorry tale."

Johnson, who won a total of five gold medals in three Olympics, has never been linked to any use of illegal substances.

But the Harrisons and Jerome Young -- a member of the relay team who ran in the Sydney Games' qualifying heats -- have been banned for doping in the past.

MEDAL LOST

The relay team initially lost the medal in 2004 after the Court of Arbitration ruled Young had committed a doping offence in 1999. CAS later reinstated the medals to the winning team because Young had not run in the final.

The Pettigrew case bears striking resemblance to the case of fellow American athlete Marion Jones, who was stripped of her five Olympic medals after admitting to doping last year.

Her Sydney Games 4x100m and 4x400m medals-winning relay team members also had their medals taken away after Jones' admission.

Johnson won his first gold medal at the 1992 Barcelona Olympics with a win in the 4x400m. He won a stunning 400m and 200m gold at the Atlanta 1996 Games, shattering the world record in the latter race with a time of 19.32, a record that still stands.

Nicknamed "the duck" because of his upright running style, Johnson went on to win the 4x400m and the 400m again in Sydney.

Pettigrew told the court he had received courier packages containing two illegal substances, human growth hormone and erythropoietin (EPO), that increase an athlete's muscle and endurance, which he proceeded to use.