The International Olympic Committee said Russian track cyclist Victoria Baranova was expelled after testing positive for testosterone on July 24 in Ratomka, Belarus. Her positive test had been confirmed on Friday by cycling's world governing body.
The 22-year-old Baranova was the bronze medallist in the sprint at the European championships, and the two-time under-23 European champion in both the sprint and the keirin.
The IOC said her accreditation was taken away and she was kicked out of the games. Her case was forwarded to the international federation for any further sanctions.
Colombian 400-meter runner Diego Palomeque was provisionally suspended after testing positive for testosterone on July 26 in London. The 18-year-old athlete did not start in his scheduled heat Saturday.
The IOC said a final decision on his status would be made after his backup "B'' sample is tested.
If it comes back positive, he would be thrown out of the games.
In two earlier cases, gymnast Luiza Galiulina of Uzbekistan and Albanian weightlifter Hysen Pulaku were expelled for failing pre-games tests. Galiulina tested positive for the diuretic furosemide, while Pulaku was caught for using the steroid stanozolol.
"We have shown that we take swift action, that cheats are caught and ejected from these games," IOC spokesman Mark Adams said. "I would say at this stage it's a pretty low number."
Adams said the IOC has taken 2,905 urine and blood samples — more than half the planned 5,000 for the entire games.