The International Olympic Committee stripped Ukrainian javelin thrower Oleksandr Pyatnytsya of his silver medal from the 2012 Olympics after a retest showed he tested positive for drugs.
The committee said on August 9 that the steroid turinabol was found in the retest and the athletics sport federation should consider imposing a two-year ban on Pyatnytsya.
The committee also said that three other athletes were caught in retests of samples from the Beijing 2008 and London 2012 games, none of them medalists. They were all banished from the Rio games, however.
They included female weightlifters Hripsime Khurshudyan of Armenia and Nurcan Taylan of Turkey, and Belarusian hammer thrower Pavel Kryvitksi.
The committee has conducted a series of retests on Olympic samples, which are stored for 10 years, using new scientific methods.
In total, 98 athletes have tested positive in two rounds of retests from the two games.
The committee said it would conduct four waves of retests in all from 2008 and 2012 "to provide a level playing field for all clean athletes."
At the Rio games, which opened on August 5, the committee is conducting 5,500 doping tests, including for the top five finishers and two randomly chosen athletes from every event.
Based on reporting by Reuters, dpa, AP, and AFP