Shot putter stripped of gold medal for doping

Colin Moynihan:The BOA chairman is stepping down after seven years (PA)

The Belarusian shot putter Nadzeya Ostapchuk was yesterday stripped of her gold medal after becoming the first athlete to test positive for a performance-enhancing substance during the London Olympics.

The 31-year-old won the shot put last Monday but it was revealed yesterday that two samples she provided before and after competition returned positive results for the steroid metenolone. Ostapchuk won silver at last year's World Championships and bronze in Beijing four years ago. The Belarusian Olympic Committee has been ordered to return the medal, the diploma and the commemorative pin given to medal winners.

Earlier in the Games, the Belarusian OC sent Ivan Tsikhan, a hammer thrower, home after suspicions emerged over a sample he provided in winning silver in Athens. The gold in the women's shot put now goes to Valerie Adams of New Zealand.

Seven athletes were thrown out of the Games after results of positive tests taken before competition began became known, while traces of marijuana, which is banned but not performance-enhancing, were found in a urine sample of the American judoka Nick Delpopolo. The International Olympic Committee has conducted an exhaustive Games-time testing regime, taking almost 6,000 samples, with some are still being tested. All samples from London will be kept until 2020 – the IOC is expected to announce next week some belated bans from the Athens Games following retesting.

Meanwhile, Colin Moynihan, chairman of the British Olympic Association, is to step down, in the wake of Britain's spectacularly successful Games, a year ahead of schedule. He will remain in the post until November while an election to choose his successor is undertaken.

"I strongly believe that this is the right time: a new chair must have the opportunity to play a central role in the future strategy of the BOA, and he or she must be integrally involved in the preparations for Sochi which is only just over 18 months away," said Lord Moynihan, who was appointed in 2005.

Contenders for the job include David Hemery, the former Olympic hurdler, and Richard Leman, president of Great Britain Hockey.