World Anti-Doping Agency President John Fahey on Tuesday announced the results of a program designed to test athletes under suspicion before they arrived in London.
In the six months to mid-June, at least 107 athletes drew doping bans, ruling them out of the games. Fahey acknowledged that perhaps not all would have qualified to compete.
"Had that been their ambition, then I am pleased to say that they are not with us in London," Fahey told the International Olympic Committee's annual gathering.
Sweeping drug cheats out of the Olympics was achieved by sharing intelligence between WADA, sports federations and London organizers, Fahey said. He promised no letup during the games, which open Friday.
"Doping athletes should know that their chances of avoiding detection are the smallest they have ever been," the WADA leader said.
The IOC plans to conduct more than 5,000 doping tests during the official Olympics period, which began when the athletes' village opened July 16.
The first 300 such tests were all negative, IOC spokesman Mark Adams said Tuesday.
Samples taken at the Olympics are kept for eight years to allow for retesting if new detection methods are developed.
In retests of samples from the 2004 Athens Olympics, the IOC has identified five possible positive results that require further investigation.
Formal cases are unlikely to be opened before the London Olympics close Aug. 12 — leaving less than three weeks before an eight-year statute of limitations expires Aug. 29.
"My guidance is that there won't be an announcement during these games," Adams said.