The results came in the second wave of tests carried out by the International Olympic Committee (IOC) on samples from the London and Beijing Olympics.
None of the medallists from London were due to compete in Rio next month.
The International Weightlifting Federation (IWF) said 11 of its competitors had tested positive.
They include Russian London 2012 silver medallists Alexandr Ivanov, Svetlana Tsarukaeva and Natalya Zabolotnaya.
Armenia's Hripsime Khurshudyan, Moldova's Cristina Iovu and Iryna Kulesha of Belarus - all of whom won bronze medals four years ago - also returned positive tests.
The IWF has imposed mandatory provisional suspensions on all 11 athletes, including Georgia's Rauli Tsirekidze, who was due to compete in Rio.
The other four weightlifters to fail tests were Russia's Andrey Demanov, Turkey's Sibel Simsek, Kazakhstan's Almas Uteshov and Azerbaijan's Intigam Zairov.
All of the athletes tested positive for the banned anabolic steroid dehydrochlormethyltestosterone.
On the day the IOC announced the second wave of results, Turkish weightlifter Sibel Ozkan was stripped of the silver medal he won in Beijing.
Six London 2012 weightlifting medallists were among the 45 athletes who last week failed retrospective drug tests, says the sport's governing body.