London: In a major doping crackdown stretching back eight years, 31 athletes in six sports were caught in retesting of samples from the 2008 Beijing Olympics and other positive cases could emerge from the 2012 London Games, the IOC said yesterday.

The International Olympic Committee opened disciplinary proceedings 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. The positive cases emerged from the recent retesting of 454 doping samples from Beijing 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.