Darya Pishchalnikova failed a drugs test ahead of this summer's Olympic Games, it has been revealed.
It has been confirmed that the Russian athlete tested positive for an anabolic steroid from a sample taken in May this year.
The 27-year-old won the silver medal in London, and is the reigning world discus champion.
The governing body of world athletics, the IAAF, has opened an investigation.
Pishchalnikova faces a life ban if found guilty, having already served a ban for doping ahead of the 2008 Olympics in Beijing.
She denies any wrongdoing.