Darya Pishchalnikova could be stripped of the silver medal she won in the discus at the London Olympics and face a lifetime ban following a positive doping test.
Russia's All Sports agency said Pishchalnikova tested positive for the banned substance Oxandrolone in a reanalysis of a sample taken in an out-of-competition control last May. The original test was found negative, but her sample was checked again months later based on a more advanced testing method introduced by the World Anti-Doping Agency.
All Sports said the retest showed the presence of Oxandrolone in Pishchalnikova's "A" sample. Testing of the backup "B" sample on November 20 also came back positive.
The positive test means Pishchalnikova could be retroactively disqualified from the London Games, where she finished second behind Croatia's Sandra Perkovic.
If the Russian is stripped of her medal, the silver will go to Li Yanfeng of China and the bronze to Cuba's Yareli Barriosnikova.
It is Pishchalnikova's second doping violation in five years, meaning she faces a lifetime ban if found guilty.
She was among seven female Russian athletes found guilty of manipulating drug samples before the 2008 Beijing Olympics, and served a ban of two years and nine months.
Pishchalnikova would be the third athlete from the London Games to lose a medal because of doping.
Nadzeya Ostapchuk of Belarus was stripped of gold in the women's shot put after testing positive for the steroid metenolone. Last month, the IOC stripped Uzbekistan wrestler Soslan Tigiev of his bronze in the 74kg class after a positive test for the stimulant methylhexaneamine.
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