By Karolos Grohmann
LAUSANNE, Switzerland (Reuters) - Four 2004 Athens Olympic medalists, including Ukraine's shot put champion Yuriy Bilonog, have been stripped of their medals after re-tested samples stored for eight years proved positive, the International Olympic Committee (IOC) said on Wednesday.
The other athletes were women's shot putter Svetlana Krivelyova of Russia and discus thrower Irina Yatchenko of Belarus, who both won bronze medals, and Belarussian 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.
(Editing By Alison Wildey and Clare Fallon)