Rio 2016: Wada publishes report highlighting 'serious failings' at Olympic Games
A Wada report on the anti-doping methods employed at Rio 2016 has highlighted "serious failings".
The World Anti-Doping Agency said many athletes who had been targeted for testing "simply could not be found".
It added that, on some days, "up to 50% of tests were aborted".
Its 55-page Independent Observers report found that, of the 11,470 athletes, 4,125 had no record of any testing in 2016, of whom 1,913 were competing in 10 "higher-risk sports".