The U.S. 4x400m relay team that won gold at the Sydney Games in 2000 has been stripped of their medals after Antonio Pettigrew admitted to doping, the International Olympic Committee (IOC) said on Saturday. Reallocation of the medals was not discussed at the IOC's executive board meeting in Beijing, the IOC's communications director Giselle Davies told reporters. Former world 400 metres champion Pettigrew, now retired, admitted in May during the trial of former coach Trevor Graham that he had used performance-enhancing drugs for about six years. His admission has led to U.S. Olympic champion Michael Johnson to say he was returning his Sydney Games relay gold medal after he felt he had not won it legitimately. The Sydney 2000 Games gold-winning relay team included Johnson and twins Alvin and Calvin Harrison. Johnson had won five Olympic gold medals but told Reuters in an interview recently he now had to be known as a four-time Olympic gold medalist. Pettigrew’s admission came during the last day of testimony for the government in the trial of his former coach, Trevor Graham, who is accused of lying to federal authorities investigating doping in sports. Graham has pleaded not guilty. It was also revealed Thursday that Olympic sprint champion Justin Gatlin worked undercover for authorities investigating doping in sports, according to the testimony of IRS agent Erwin Rogers. Rogers testified that Gatlin, who once shared the world record in the 100 meters, secretly recorded several telephone calls with Graham. U.S. District Judge Susan Illston barred Rogers from disclosing any more details of the calls. Gatlin, who has served half of a four-year ban for doping, tested positive for excessive testosterone at the Kansas Relays in 2006, his second doping violation. He has maintained he never knowingly took a performance-enhancing drug. Gatlin has asked the Court of Arbitration for Sport to cut his suspension nearly in half so he can compete at the Beijing Olympics. Gatlin, like Pettigrew, was once a member of Graham's Sprint Capitol USA team in Raleigh, N.C., which also included sprinters Marion Jones and Tim Montgomery — both of whom are now imprisoned. Pettigrew testified that Graham encouraged him in 1997 to inject human growth hormone and the oxygen-boosting drug EPO, both banned in track. Soon after, Pettigrew said, he began buying the drugs from Angel "Memo" Heredia, an admitted steroids dealer from Laredo, Texas.