The International Olympic Committee has announced that a total of 23 competitors at London 2012 have failed retrospective doping tests.
Olympic chiefs carried out the retests using the latest scientific methods available, focusing solely on the athletes who were in line to compete at this year's Games in Rio.
A total of 454 doping samples from the 2008 Beijing Games and a further 265 from the most recent Olympics were retested, with the 23 athletes in question coming from six different countries.
"These re-analyses show, once again, our determination in the fight against doping," IOC president Thomas Bach said in a statement. "We want to keep the dopers away from the Olympic Games in Rio de Janeiro."
It was revealed last week that 31 athletes doped at the 2008 Games following a re-examination of the samples provided - 14 of which concerned Russian athletes, including medallists.