The International Olympic Committee (IOC) has revealed that 23 athletes from the 2012 London Olympic Games have tested positive for banned substances following reanalysis of doping samples.
It was announced by the IOC last week that 31 athletes could be banned from competing at the Rio Olympics in August following retests of samples taken from the 2008 Games in Beijing.
Further analysis of 265 selected samples from the London Games has returned 23 Adverse Analytical Findings (AAFs) from athletes in five sports from six nations, with more results to come.
IOC president Thomas Bach said: "These reanalyses show, once again, our determination in the fight against doping.
"We want to keep the dopers away from the Olympic Games in Rio de Janeiro.
"This is why we are acting swiftly now. I have already appointed a disciplinary commission, which has the full power to take all the decisions on behalf of the IOC."
The Russian Olympic Committee (ROC) on Tuesday confirmed 14 athletes who represented the country at the Beijing Games failed drugs tests when re-examinations were carried out.
The IOC last week also announced plans to investigate claims from the head of Russia's anti-doping laboratory at the 2014 Winter Olympics in Sochi that certain athletes from the country were part of a state-sponsored doping program to maximise home success.