The International Olympic Committee notified the U.S. Olympic Committee by letter that the 4x100 relay team has been disqualified and all the medals withdrawn. The letter asks the USOC to collect the medals and return them to the IOC.
"As expected, following USADA's decision in the Tyson Gay case, the IOC today confirmed that the U.S. team has been disqualified from the 4x100-meter race that was part of the athletics competition at the London 2012 Olympic Games," USOC spokesman Patrick Sandusky said in a statement.
"We will begin efforts to have the medals returned, and support all measures to protect clean athletes."
The USOC statement came after The Associated Press broke the news of the disqualification.
Gay returned his own medal last year after accepting a one-year doping suspension and the loss of results going back to July 2012, but the status of the U.S. second-place finish in London and the medals of Gay's relay teammates had remained in limbo until now.
Under international rules, an entire team can be disqualified and stripped of medals because of doping by one member.
Gay was a member of the American team that finished second in London behind a Jamaican team anchored by Usain Bolt. The Americans set a national record in the final with a time of 37.04 seconds.
The other U.S. team members losing medals are Trell Kimmons, Justin Gatlin, Ryan Bailey, Jeffery Demps and Darvis Patton. Kimmons, Gatlin and Bailey ran in the final with Gay.
Gatlin, who is in Qatar for the opening Diamond League meet of the season on Friday, told the AP he was not aware of the decision and had no comment. Gatlin, who won the 100-meter gold medal at the 2004 Athens Games, served a four-year doping ban from 2006.
Gay tested positive for steroids at the U.S. championships in 2013. He received a reduced suspension — rather than a two-year ban — because he co-operated with the U.S. Anti-Doping Agency's investigation that led to an eight-year ban for his former coach, Jon Drummond.
Gay's results were annulled going back to July 15, 2012, the date when he first used a product containing a banned substance.
If the London medals are reallocated, the silver will go to Trinidad and Tobago, which finished third in 38.12 seconds. The bronze would go to the French team which placed fourth in 38.16 seconds.
The rules of track and field's world governing body, the International Association of Athletics Federations, mandated that the entire U.S. team be disqualified, but the final decision was up to the IOC.
Drummond was the coach of the U.S. relay team in London and placed Gay on the team. According to the USADA decision in Drummond's case, the athlete took a banned substance in July 2012 with the coach's knowledge.
The IOC has previously stripped U.S. relay teams of medals retroactively for doping, including three teams from the 2000 Sydney Olympics.
The U.S. was stripped of gold in the women's 4x400 and bronze in the 4x100 following Marion Jones' admission of doping. Jones returned her medals, but her teammates appealed to the Court of Arbitration for Sport to keep theirs and won their case in 2010. The court said IAAF rules at the time did not allow entire teams to be disqualified because of doping by one athlete.
The IOC also stripped the U.S. men's 4x400 relay of their Sydney gold after a doping admission by Antonio Pettigrew.
In 2012, American runner Crystal Cox was stripped of her gold medal from the 4x400 relay at the 2004 Athens Olympics after admitting to doping. The IOC did not disqualify the rest of the team because it was unclear which rules were in effect at the time.
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AP Sports Writer Gerald Imray in Doha, Qatar, contributed to this report.