The IOC says 23 athletes have tested positive in reanalysis of their doping samples from the 2012 London Olympics.
The International Olympic Committee announced the results Friday after retesting 265 London samples with improved techniques.
The IOC says the athletes represent five sports and six countries. It did not name them.
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The London athletes are in addition to the 31 caught in retests of samples from the 2008 Beijing Olympics. The Russian Olympic Committee has confirmed that 14 of those athletes were Russians.
The IOC still has to retest the athletes' "B'' samples. Formal positive cases are not declared until the "B'' samples confirm the original findings.
The IOC said the retests targeted athletes who were hoping to compete at the Olympics in Rio de Janeiro in August.