By Martyn Herman LONDON (Reuters) - Thirty one athletes from six sports could be banned from this year's Rio Olympics after failing dope tests when 454 samples were reexamined from the 2008 Beijing Games, the International Olympic Committee said on Tuesday. The IOC also said it would start re-testing Sochi 2014 winter Games samples after allegations of tarnished samples were made last week by Russia's former top anti-doping scientist. Some 250 samples from the London Games will also be reexamined.
