Negative publicity could harm Phelps's lucrative sponsorship deals
The International Olympic Committee has accepted an apology from US swimmer Michael Phelps, photographed with a kind of pipe used for smoking cannabis.
The IOC said it had no reason to doubt Phelps's sincerity or commitment to acting as a role model.
The Olympic star has apologised for his "regrettable behaviour", but did not say whether he had taken drugs.
A British paper said the picture was taken three months after he won eight gold medals at last year's Olympics.
The 23-year-old was caught on camera inhaling from a type of glass pipe which can be used for smoking cannabis.
The photo, which appeared in Britain's News of the World newspaper, was said to have been taken at a student party last November when Phelps was on a long break from training.
His actions should have no impact on the medals he won at Beijing, as smoking cannabis out of competition is not an offence under sport's international doping laws.
But the mistake could still prove costly as Phelps is a high-profile athlete with lucrative sponsorship deals, says BBC sports reporter Alex Capstick.
Negative publicity could damage those contracts, he adds.
Phelps, the most successful Olympian of all time, has also escaped punishment by the United States Olympic Committee.
US officials said the news was disappointing but they expected him to move on and to set the type of example expected from a great Olympic champion.