The IOC says the 31 unnamed athletes come from 12 countries and six sports – with all those confirmed to have broken rules being banned from this summer’s Games.
The governing body said it is further awaiting the results of 250 re-tests from the London Olympics of 2012.
Tokyo 2020
Team GB say athletes likely to be vaccinated before Tokyo
A statement read: "The International Olympic Committee (IOC) retested 454 selected doping samples from the Olympic Games Beijing 2008. The re-tests follow work with the World Anti-Doping Agency (WADA) and the International Federations.
They were focused on athletes who could potentially start at the Olympic Games Rio 2016 and were conducted using the very latest scientific analysis methods.
"As a result up to 31 athletes from six sports could be banned from competing at the Olympic Games in Rio. The Executive Board of the IOC today agreed unanimously to initiate proceedings immediately, with the 12 NOCs concerned informed in the coming days. All those athletes infringing anti-doping rules will be banned from competing at the Olympic Games Rio 2016."

31 athletes could miss Rio as Beijing drug tests re-examined

Sochi action announced

2014, Olympics Sochi (AFP)

Image credit: AFP

The IOC also announced its response to allegations in the New York Times that Russia conducted a sophisticated and widespread doping operation at the Sochi Winter Games of 2014 which violated the integrity of the anti-doping laboratory on site.
The New York Times alleged that "at least 15 medal winners, were part of a state-run doping program, meticulously planned for years to ensure dominance at the Games, according to the director of the country’s anti doping laboratory at the time."
The IOC said in Tuesday's statement: "Swift and decisive action will also follow the controversy surrounding the anti-doping laboratory in Sochi. Meeting Tuesday, the EB of the IOC has requested WADA to initiate a fully fledged investigation into allegations that testing at the Sochi Laboratory was subverted.
"The IOC for its part will instruct the Lausanne Anti-Doping Laboratory, where the Sochi samples are stored for 10 years, to proceed in cooperation with WADA with their analysis in the most sophisticated and efficient way possible. Also, the IOC has already requested the Russian Olympic Committee to undertake all efforts to ensure the full cooperation of the Russian side in the WADA investigation."
Russia has denied the allegations, with a spokesperson for president Vladimir Putin calling them "absolutely groundless".

IOC president: A powerful strike against cheats

Thomas Bach, le président du CIO

Image credit: AFP

IOC president Thomas Bach said: "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 re-tests 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 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 competitions, including the Rio anti-doping laboratory, so that the Olympic magic can unfold in Rio de Janeiro.”
Tokyo 2020
Rugby gets Tokyo test events back under way
Tokyo 2020
'I was just going to be a gardener' - Team GB windsurfer Squires realising Olympic dream