In a major doping crackdown stretching back eight years, 31 athletes in six sports could be barred from competing in this year's Olympics after they were caught in retesting of drug samples from the 2008 Beijing Games, and other positive cases could emerge from the 2012 London Games.
The International Olympic Committee opened disciplinary proceedings yesterday against the 31 unidentified athletes from 12 countries who competed in Beijing and were planning to take part in the Rio de Janeiro Games in August.
"This is a powerful strike against the cheats," IOC President Thomas Bach said. "They show once again that dopers have no place to hide."
The IOC said it also planned to reanalyze drug tests from the 2014 Sochi Winter Games after allegations samples were tampered with as part of a state-sponsored Russian doping program.
The positive cases from Beijing emerged from the recent retesting of 454 doping samples with "the very latest scientific analysis methods," the IOC said.
The Olympic body stores samples for 10 years to allow for retesting with improved techniques, with athletes caught facing retroactive disqualification and loss of any medals.
The IOC said it could not immediately identify the athletes caught in the Beijing retests for legal reasons, saying it would inform the relevant national Olympic committees in the coming days.
"All those athletes infringing anti-doping rules will be banned from competing at the Olympic Games" in Rio, the IOC said after a teleconference meeting of its policy-making executive board.
Results of retesting of 250 samples from the London Olympics will be announced shortly, the IOC said. Those tests were also aimed at athletes planning to compete in Rio.
The IOC said it would also undertake a "wider retesting program" of medalists from both the Beijing and London Games.
Samples of athletes who could be promoted to medals following disqualification of drug cheats will also be retested.