Forty-five athletes have failed dope tests after their samples from the 2008 Beijing Olympics and the 2012 London Games were re-analysed, the International Olympic Committee (IOC) said on Friday.
The results are from a second wave of retests and take the total number of athletes who tested positive for prohibited substances to 98, the IOC added in a statement.
Of the 45 failed tests announced on Friday, 30 were from Beijing, including 23 medallists, and 15 were from London. The IOC did not say if any of the London athletes had won medals.
“The new reanalysis once again shows the commitment of the IOC in the fight against doping,” IOC President Thomas Bach said.
The IOC stores samples for a decade in order to re-test using newer methods or to look for new drugs.
The results are part of the IOC's retesting of samples from past Games to keep cheats from competing at the Rio de Janeiro Olympics in August.
The third and fourth waves of tests are expected to continue throughout and after the Rio Games.
The IOC said it was informing the national Olympic committees and international sports federations affected by the latest positives, clearing the way for disciplinary proceedings to begin against the athletes.
The IOC said it could not provide more details, including the names of the athletes, "for legal reasons."
"This will follow in due course," it said.
So far, only one athlete has been formally disqualified by the IOC in the retesting program.
Last week, Ukrainian weightlifter Yulia Kalina was stripped of her bronze medal from the London Olympics after her sample came back positive for the steroid turinabol.
The IOC reported in May that it had found 31 positives from Beijing. It said Friday that the backup "B'' samples in two cases did not confirm the original finding, while an additional positive case was confirmed later.
