The International Olympic Committee could ban up to 31 athletes who potentially could have competed at this year’s Rio Olympics after retesting 454 doping samples from the 2008 Beijing Games. The athletes, as yet unnamed, represent 12 nations and competed in six sports. They will be subject to disciplinary hearings and will be banned from Rio if found to have broken anti-doping rules.

In a news release, the IOC said it retested the samples using “the very latest scientific analysis methods.” It also said it is retesting 250 samples from the 2012 London Olympics.

The official slogan of the 2008 Games was “Zero Tolerance for Doping” and officials conducted 4,770 doping tests, at the time the most in Olympic history. Six eventually had their medals taken away, either because of anti-doping tests conducted at the Games themselves, retesting of samples conducted in 2009 or, in one case, a retroactive ban after Georgian shot-putter Andrei Mikhnevich had his samples from the 2005 world championships retested (his results from 2005 onward were nullified). The Norwegian men’s show-jumping team was stripped of its bronze medal after the horse ridden by Tony Andre Hansen was found to have prohibited capsaicin in its urine.

Olympic doping samples are kept for 10 years at a laboratory in Switzerland.

The IOC also announced Tuesday that it has asked the World Anti-Doping Agency to conduct an investigation into an alleged state-run doping scheme initiated by the Russian government at the 2014 Sochi Games. Last week, the New York Times revealed that the head of Russia’s anti-doping agency — who has since fled to the United States for fears of his safety — initiated an elaborate plan to subvert anti-doping measures, first by concocting a steroid-liquor cocktail that sped up absorption of the performance-enhancing drugs, then by swapping out Russian athletes’ dirty urine with clean urine at the Sochi Olympics.

Russian athletes led the Sochi medal table with 33, 13 of them gold, after finishing a disappointing sixth in the medal chase four years earlier in Vancouver.

“All these measures are a powerful strike against the cheats we do not allow to win. They show once again that dopers have no place to hide. The retests from Beijing and London and the measures we are taking following the worrying allegations against the Laboratory in Sochi are another major step to protect the clean athletes irrespective of any sport or any nation. We keep samples for ten years so that the cheats know that they can never rest,” IOC President Thomas Bach said in the release. “By stopping so many doped athletes from participating in Rio we are showing once more our determination to protect the integrity of the Olympic competitions, including the Rio anti-doping laboratory, so that the Olympic magic can unfold in Rio de Janeiro.”

In non-doping news, the IOC said it will not take any action against Tokyo 2020 organizers until France’s justice department completes its investigation into alleged improprieties concerning the bidding process for those Olympics. French investigators are looking into whether two high-ranking world track and field officials had funneled bribes from the cities that bid for the 2016 and 2020 Olympics to a group of International Olympic Committee members. They have uncovered nearly $1.5 million in payments sent from Tokyo’s 2020 Olympic bidding team to an account linked to Lamine Diack, the former president of the International Association of Athletics Federations and a former International Olympic Committee member, contending that Diack acted as a middleman between the bid team and the IOC members.

Tokyo 2020 organizers have since said the $1.5 million payment was for legitimate consulting work.