Russian track cyclist Victoria Baranova has been expelled from the London Olympics after testing positive for the male hormone testosterone.
The 22-year-old was due to compete in Friday's women's keirin competition but was sent home earlier this week.
Baranova failed an International Olympic Committee (IOC) pre-Games drugs test in Belarus on 24 July.
"She has admitted to taking a banned substance," the International Cycling Union (UCI) confirmed.
UCI spokesman Enrico Carpani said: "We have been working closely with the IOC and we are very happy with this collaboration, which strengthens our fight against doping."
A hearing had been planned for Friday but it was cancelled after Baranova admitted the violation.
Commenting on Baranova's admission, BBC Sport analyst and world champion Mark Cavendish said: "It is frustrating.
"Our sport has been dragged through a lot, really dragged through the mud. It is always in the spotlight.
"It really winds me up. It's not only cycling, but this is a cyclist. We have to put up with the questions and everything. It's really disappointing."
Baranova is the latest athlete to be expelled from London 2012.
Albanian weightlifter Hysen Pulaku was the first to be ejected from the Games after testing positive for the steroid stanozolol.