Belarus shot putter Nadezhda Ostapchuk has been stripped of the women's Olympic title after failing a drugs test, elevating New Zealander Valerie Adams to champion, 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.
"The athlete was first requested to provide a urine sample for a doping control on 5 August," the IOC said.
"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 Adams with Russia's Yevgeniya Kolodko now taking silver and Lijiao Gong of China bronze.
Ostapchuk, the 2005 world champion, took 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 managed 20.70m.