LONDON (AP) — Six athletes from Russia and Belarus, including three gold and two silver medalists, have been caught for doping in retests of their samples from the 2005 track and field world championships in Helsinki.

Nazdeya Ostapchuk, a Belarusian shot putter who was also stripped of her London Olympic gold medal for doping, was one of the six named Friday by the IAAF. She won the shot put at the 2005 worlds and finished second in 2003, 2007 and 2011.

The other two gold medalists from 2005 were the hammer throwers, men's winner Ivan Tsikhan of Belarus and women's champion Olga Kuzenkova of Russia.

Tsikhan won the Olympic bronze medal in 2008, and originally finished second at the 2004 Athens Games before being stripped of his silver medal for doping. He also won gold at the 2003 and 2007 world championships. Kuzenkova won the Olympic gold medal in 2004.

The other three are: Vadim Devyatovskiy of Belarus, who took second in the hammer at the 2005 worlds; Tatyana Kotova of Russia, who was second in the long jump; and Andrei Mikhnevich of Belarus, who was sixth in the shot put but won gold in the event at the 2003 worlds.

The IAAF said it was opening disciplinary procedures against the six. It did not say for what substances the athletes tested positive, nor what the punishments could be. If found guilty of doping, they face being stripped of their medals and results and could be suspended for two years or more.

"The IAAF's message to cheaters is increasingly clear that, with constant advancements being made in doping detection, there is no place to hide," IAAF President Lamine Diack said in a statement. "The IAAF will continue to do everything in its power to ensure the credibility of competition, and where the rules have been broken, will systematically uncover the cheats."

Frozen samples from Helsinki were re-tested by the IAAF just within the eight-year statute of limitations for drug violations laid down by the World Anti-Doping Code.

The IAAF said it retested samples using "the most up-to-date analytical techniques."

If Tsikhan and Devyatovskiy are stripped of their medals, then Szymon Ziolkowski of Poland would stand to be moved up to gold. Yipsi Morena of Cuba was second to Kuzenkova in the women's hammer and could be upgraded, while Olga Ryabinkina of Russia could get gold and Valerie Adams of New Zealand silver in the women's shot put if Ostapchuk loses her medal.

Ostapchuk was stripped of her London Olympic gold medal in August, only hours after the closing ceremony.

The IOC said she tested positive for steroids both before and after winning the shot put. The gold medal was later awarded to Valerie Adams of New Zealand.

In an email to The Associated Press last week, IAAF deputy general secretary Nick Davies confirmed the announcement last month by Russia's Anti-Doping Agency that it provisionally suspended Kotova for failing a test at the 2005 worlds.

Two other athletes previously had their performances annulled at the 2005 worlds for doping, hammer thrower Vladislav Piskunov of Ukraine and discus thrower Neelam Jaswant Singh of India.