Paris - Belarus' Nadezhda Ostapchuk has been stripped of the women's Olympic shot put title after failing a drugs test, the International Olympic Committee (IOC) said in a statement on Monday.
The 31-year-old, who provided two urine samples which contained the banned anabolic agent metenolone, becomes the first medallist of the London Games to test positive for a banned substance.
An IOC statement said: "The International Olympic Committee (IOC) on Monday announced that it has disqualified, withdrawn the medal from, and excluded Belarus's Nadzeya Ostapchuk (athletics, women's shot put) from the Games of the XXX Olympiad in London.
"The athlete was first requested to provide a urine sample for a doping control on August 5. She competed the next day in the women's shot put event, where she placed first, and was asked to provide a sample straight after her competition.
"Both samples indicated the presence of metenolone, which is classified as anabolic agent under the 2012 Prohibited List."
The gold medal will be awarded to Valerie Adams of New Zealand, with Russia's Yevgeniya Kolodko now taking silver and Lijiao Gong of China bronze.
Ostapchuk, the 2005 world champion, took a surprise gold with a throw of 21.36m to end the almost two-year unbeaten run of defending Olympic and three-time world champion Adams, who took silver with 20.70m.
The Belarussian was competing in her third Olympics in London. She finished fourth in Athens in 2004 and won bronze in Beijing four years ago.