A total of 23 athletes from five sports tested positive for banned drugs in re-checks of 265 samples from the London 2012 Olympics, the International Olympic Committee said on Friday.
The IOC said the athletes were members of six different national Olympic Committees four years ago.
Last week the organisation found 31 athletes from six sports who could be banned from the Rio de Janeiro Games in August after failing doping tests when 454 samples were re-examined from the 2008 Beijing Olympics.
The IOC, which said one more sample from Beijing had shown "abnormal parameters" and would also be followed up on, added that the re-testing programme was ongoing and could deliver more positive checks in the coming weeks.
"These re-analyses show, once again, our determination in the fight against doping," said president Thomas Bach.
"We want to keep the dopers away from the Olympic Games in Rio de Janeiro.
"I have already appointed a disciplinary commission which has the full power to take all the decisions on behalf of the IOC."
