Two officials with knowledge of the decision tell The Associated Press that the IOC disqualified Soslan Tigiev, a freestyle wrestler who won bronze in the 74-kilogram class.
The officials spoke to the AP on condition of anonymity because the ruling hasn't been announced yet.
The officials say Tigiev tested positive for the banned stimulant methylhexaneamine. The result was confirmed after the games finished Aug. 12.
Tigiev becomes the second athlete from the London Olympics stripped of a medal after a doping violation.