LONDON -?Colombian 400 metres runner Diego Palomeque Echevarria has been temporarily banned from the London Games following a positive test for a prohibited substance, the International Olympic Committee confirmed on Saturday.

Brazilian female rower Kissya Cataldo da Costa has also been expelled from the Olympics for failing a dope test for EPO, a Brazilian rowing team official told Reuters. ?

Palomeque has been the fourth athlete to have been suspended, provisionally or permanently by the IOC, since the start of the Olympic period on July 16 though several other athletes have been comfirmed as positive by their own federations.

Russian cyclist Victoria Baranova, who has already been sent home, has been officially expelled following a July 24 positive test for testosterone in Belarus.

The 22-year-old Baranova, ranked two in the world in keirin, was a medal contender in London.

"I do not think this changes where we are at all," IOC spokesman Mark Adams told reporters when asked whether the latest positive tests were showing a wider use of banned substances at the Games than expected.

"Cheats are being caught and ejected."