The International Olympic Committee (IOC) said on Friday it had stripped one athlete of his bronze medal and retrospectively punished two others after doping retests of samples from the 2012 London Games.
The International Testing Agency (ITA) has been selecting competitors from the London Olympics for re-analysis before the statute of limitations is reached in 2020.
Among the latest positives were Valentin Hristov of Azerbaijan, who finished third in the men's 56kg weightlifting, and becomes the ninth lifter from those Games caught by retests since last autumn. He tested positive for an anabolic steroid, Turinabol.
The other positives came from two Belarusian track and field athletes who did not make it past the qualifying stages of their events.
Anis Ananenka, eliminated in the men's 800 metre heats, also tested positive for Turinabol. Alena Matoshka, who came 25th in the women's hammer, tested positive for anabolic steroid Oxandrolone.
All three can appeal, either to the Court for Arbitration in Sport or an IOC Disciplinary Commission.
The IOC said in a press release that ITA had taken over "the selection of samples to be re-analysed and the results management."