The International Olympic Committee has barred Albanian weightlifter Hysen Pulaku in the first official doping ban after the start of the London Games.
The IOC said Pulaku tested positive for a banned steroid, stanozolol, on July 23, and that a backup ''B'' sample confirmed the result.
The announcement came a day after Albania dropped the 19-year-old from its weightlifting team over doping suspicions.
He was supposed to have competed in the 77-kilogram category.
In a hearing Thursday the lifter's coach and uncle, Sami Pulaku, ''explained that neither he nor the athlete understood how such substance ended up in the body of the athlete,'' the IOC said.
Two Turkish lifters were also dropped by their federation at the last minute after failing doping tests.
The weightlifting competition begins Saturday with the women's 48-kilogram category.
Weightlifting has a troubled history when it comes to doping.
Despite attempts to clean up the sport, several top competitors have tested positive in recent years, including former Olympic and world champion Nurcan Taylan of Turkey and Liao Hui, the 2008 Olympic champion in the men's 69-kilogram class.
Both are serving doping bans and will miss the London Games.