Belarusian shot-putter Nadzeya Ostapchuk could be awarded an Olympic bronze medal after a 2004 Athens Olympic medallist was stripped of her medal after re-tested samples stored for eight years proved positive.
Ostapchuk was stripped of her gold medal from this year's Olympics after she failed a drug test, with New Zealand's Valerie Adams awarded the gold.
The Belarusian was banned for a year, but may end up with an Olympic medal after Russian Svetlana Krivelyova was stripped of her bronze medal from Athens where Ostapchuk finished fourth. Adams finished eighth at the 2004 Olympics.
Three other 2004 Athens Olympic medallists have also been stripped of their medals. The other athletes are Ukraine's men's shot put champion Yuriy Bilonog, discus thrower Irina Yatchenko of Belarus and Belarusian hammer thrower Ivan Tsikhan who took silver.
Three-times world champion Tsikhan had also lost his bronze medal from the 2008 Beijing Games but that decision was overturned at the Court of Arbitration for Sport (CAS) because of a laboratory procedural error.
A case involving a fifth unnamed athlete from the Athens Games was still pending, the IOC said.
The four named athletes tested positive for anabolic steroids when some 100 samples from the Games eight years ago were target-tested by the IOC using modern methods earlier this year.
The IOC stores samples for eight years to allow for re-testing for newly discovered substances or for substances for which there was no test available at the time.
"You always want to wait until science gives you the most sensitive tests," IOC President Jacques Rogge told reporters. "When we retested the athletes for Athens they had undergone testing that was negative (during Athens)."
"Since then there has been progress, we were informed about better tests and new tests. The more time you have, the bigger the chances that science will deliver better tests."
Rogge said it was now up to the respective federations to see that the medals were returned and change the results before the IOC proceeded with reawarding the medals.
With Bilonog losing his gold, doping has now claimed both men's and women's shot put winners of the competition staged at ancient Olympia, a venue chosen to take the modern Games back to its ancient roots.
The event was one of the most spectacular of the Games, with the shot put competition staged inside the ancient Olympic stadium.
Russian Irina Khorzanenko lost her shot put medal after testing positive for the steroid stanozolol.
The total tally of doping cases from the Athens Olympics is now 31 after 26 positive tests at the time, which was the most in any Games.
Rogge said he would be happy to extend the statute of limitation past the current eight years, adding that the World Anti-Doping Agency (WADA) was considering making it 10 years.
"There is a proposal in the amendments of the WADA code to extend it to 10 years," the Belgian said.
"That would give us more leeway to handle (cases). It remains to
be seen if the samples can sustain so long a period, this is
something that we will have to see," said Rogge, who introduced
zero tolerance on doping and is stepping down next year.