LAUSANNE, Switzerland — Two Belarusian hammer throwers were stripped of their Olympic silver and bronze medals for doping on Thursday, nearly four months after the Beijing Games. A Polish canoeist was also disqualified for drug use.

The International Olympic Committee executive board ruled against Vadim Devyatovskiy and Ivan Tsikhan, who tested positive for abnormal levels of testosterone after finishing 2-3 in the Aug. 17 hammer final at the Bird's Nest stadium.

The silver now goes to Krisztian Pars of Hungary and the bronze to Koji Murofushi of Japan. Slovenia's Primoz Kozmus won the gold medal.

Devyatovskiy faces a lifetime ban from the sport with his second doping offense. He served a two-year drug suspension from 2000-02.

It's the first violation for Tsikhan, a three-time world champion and silver medalist at the 2004 Athens Olympics.

The Belarusians had denied drug use and appeared at a hearing before the IOC's disciplinary commission in Lausanne in September.

Murofushi is benefiting for a second time from a rival's doping case. Four years ago, he was upgraded to the gold medal in Athens after Hungary's Adrian Annus was stripped of first place.

Also Thursday, the IOC disqualified Polish canoeist Adam Seroczynski, who tested positive for the steroid clenbuterol in Beijing after finishing fourth in the flatwater K2 event. His teammate, Mariusz Kujawski, was not implicated.

The three cases bring to nine the number of athletes caught for doping in Beijing.

The IOC disqualified six athletes during the Aug. 8-24 Olympics — Ukrainian heptathlete Lyudmila Blonska, Ukrainian weightlifter Igor Razoronov, Greek hurdler Fani Halkia, North Korean shooter Kim Jong Su, Spanish cyclist Isabel Moreno and Vietnamese gymnast Thi Ngan Thuong Do.

Blonska was stripped of her silver medal, while Kim had his silver and bronze medals revoked.

The IOC, meanwhile, has decided to retest 500 Beijing doping samples to look for previously undetectable drugs.

Starting in January, labs will begin analyzing 400 samples for CERA, a new version of the blood-boosting hormone EPO, and 100 samples for insulin. The samples are mainly from endurance events such as cycling, rowing, swimming and track and field. The results will be known by the end of March.