IOC says it will catch Olympic drug cheats
31 July 2012 Last updated at 12:57 BST
Olympic organisers have said their drug testing programme is strong and "if there are cheats, we will catch them".
It comes after Chinese gold medallist swimmer Ye Shiwen, 16, denied taking drugs to aid her performance, saying there was "no problem with doping".
International Olympic Committee communications director Mark Adams told a news conference: "We have a very strong drugs testing programme".
Mr Adams added that the public should not be surprised if they saw big performances.
"We need to get real here; these are the world's best athletes competing at the highest level with records being broken all over the place," he said.