Thirty one athletes from six sports could be banned from competing at this year's Olympic Games in Rio de Janeiro after 454 doping samples from the 2008 Beijing Olympics were re-tested.
A statement from the International Olympic Committee (IOC) said its executive board had stepped up the fight against drugs cheats and the re-tests had been carried out in conjunction with the World Anti-Doping Agency (WADA) and international federations.
It said the re-tests were focused on athletes who could potentially take part in this summer's Rio Games.
Twelve national Olympic associations will be informed of the results in the coming days, the IOC confirmed.
Some 250 samples from the London 2012 Olympics will also be re-tested.
"All these measures are a powerful strike against the cheats we do not allow to win," IOC president Thomas Bach said in a statement.
"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."
Bach's reference to the Sochi laboratory follows allegations of systematic cheating by Russia during the 2014 Winter Olympics.
Russia was suspended by the IAAF, athletics' world governing body, in November after being accused of "state sponsored" doping in a report commissioned by WADA.
Russia's sports minister Vitaly Mutko apologised last week for the doping scandal.
A decision on whether they will be reinstated for the Rio Olympics will be announced on 17 June.