The International Olympic Committee (IOC) has announced that 31 athletes from the 2008 Beijing Olympics tested positive for doping after drug samples were retested using updated methods. Similar re-tests are under way for the London 2012 Games.
The IOC stores samples for 10 years in order to combat doping and re-tested 454 Beijingsamples from athletes who were expected to participate in the Rio Games. The plan is to ban all 31 who failed the new test; the athletes have not yet been identified.
"All these measures are a powerful strike against the cheats we do not allow to win," said IOC president Thomas Bach.
"They show once again that dopers have no place to hide. We keep samples for 10 years so that the cheats know that they can never rest.
"By stopping so many doped athletes from participating in Rio, we are showing once more our determination to protect the integrity of the Olympic competition."
The 31 athletes are from 12 different countries and participated in six different events. In addition to the 250 pending re-tests from London, the IOC will also begin a "wider re-testing program" specifically targeting medalists from Beijing and London, as well as re-tests on any would-be medalists who would move up if a previous top-three finisher is disqualified.
The IOC has begun disciplinary proceedings against the newly found athletes and will notify the appropriate national Olympic committees in the next few days.