The United States men's 4x400m relay team have been stripped of the gold medals won at the 2000 Sydney Olympics.
The decision comes in the wake of former world 400m champion Antonio Pettigrew giving up his medal after his admission of doping offences.
Pettigrew's team-mates Michael Johnson and Alvin and Calvin Harrison, who ran in the final, plus Jerome Young and Angelo Taylor, also lose their medals.
The International Olympic Committee has delayed reallocating the final places.
Nigeria finished second in the final, with Jamaica third and the Bahamas fourth.
It was the sixth American medal from the Sydney Games lost to doping in the past eight months after disgraced sprinter Marion Jones was stripped of her five medals because of her doping confession in 2007.
IOC spokeswoman Giselle Davies said the decision to withdraw the men's 4x400m golds was as a result of the ongoing investigation into the scandal surrounding the San Francisco-based Balco laboratory, responsible for providing top athletes with drugs.
606: DEBATE
"It was decided that the entire US relay team will be disqualified from the Sydney Games. It forms part of a wider piece of work on the Balco case," stated Davies.
The Bay Area Laboratory Co-Operative, or Balco, was a US company based in California that initially specialised in food supplements but would become far more famous for its sideline in performance-enhancing drugs.
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 track legend Johnson declaring he would be returning his Sydney relay gold anyway, as he feels he had not won it legitimately.
Johnson, who won five Olympic golds and who has not been linked to the use of banned substances, has insisted he now wants to be known as just a four-time champion.
Young, who ran in the Sydney preliminary rounds, had already been stripped of his medal because of a doping offence.
The United States Anti-Doping Agency has annulled all Pettigrew's competitive results since January 1997. He has also voluntarily surrendered his 1997 and 1999 World Championship relay golds.
The decision could also lead to the Americans losing their 4x400 metres world record of 2mins 54.20secs set in July 1998.
"We support the action taken by the IOC"
Pettigrew also ran in that race with Young, Tyree Washington and Johnson.
Pettigrew acknowledged using the prohibited blood booster erythropoietin (EPO) and human growth hormone (HGH) beginning on or about January 1997 through 2003.
The IOC have also disqualified Pettigrew from his seventh-place finish in the individual 400m in Sydney and have now banned him from attending the upcoming Beijing Games "in any capacity," including as a competitor, coach or technical official.
United States Olympic committee spokesman Darryl Seibel said: "We support the action taken today by the IOC.
"Athletes who make the unacceptable choice to cheat should recognise that there will be consequences. Those consequences can be severe, including the loss of medals and results.
"In other matters like this in the past we've worked with the IOC to make certain medals will be returned and we'll do so again."
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