Armed with enhanced techniques, the IOC is retesting hundreds of doping samples from the 2008 Beijing Olympics to weed out drug cheats before they can compete in this year's Summer Games in Rio de Janeiro.
In an interview with The Associated Press, IOC medical director Dr. Richard Budgett said athletes who competed in Beijing and are likely to be selected for Rio are having their stored samples reanalyzed to catch any violators who evaded detection eight years ago.
"We want to protect the clean athletes who are going to be competing in Rio," Budgett said. "We are making sure that athletes who cheated back in 2008 don't get to compete in Rio in 2016."
The International Olympic Committee stores blood and urine samples from each games so they can be reanalyzed years later with improved testing methods. Any positive tests can lead to retroactive sanctions, disqualifications and loss of medals.
The statute of limitations for retesting was extended in 2015 from eight to 10 years, meaning the Beijing samples remain valid through 2018.
"Many of the athletes who are likely to be selected for Rio will have their samples retested a couple of years earlier than we need to," Budgett told AP on the sidelines of the Tackling Doping in Sport conference in London. "There are some new analyses that are available. The samples are in the process of being retested. It's in the hundreds."
"We've co-operated very closely with the international federations, finding out which athletes are still competing, finding out which athletes are likely to be selected for Rio," he added. "If we've got samples for them from Beijing, we're doing that testing."
Budgett said the process should be completed in the next few weeks.
"If we have any adverse analytical findings, there will be a sanctioning process and those athletes will be very unlikely to compete in Rio," he said.
Samples to be retested before 2018
Noting that scientific techniques will continue to improve in the next two years, the IOC is keeping the other Beijing samples for retesting closer to the 2018 deadline, Budgett said.
It's not the first time that samples from Beijing have been retested. A few months after those games, the IOC reanalyzed nearly 1,000 of the total of 4,000 samples with a new test for the blood-boosting drug CERA. Five athletes were caught, including 1,500-metre gold medallist Rashid Ramzi of Bahrain.
Budgett said some samples from the 2012 London Olympics are also being retested now on a targeted basis ahead of the Rio Games, although most are being saved for later reanalysis.
"We want to reserve samples for the expected advances that will happen over the next six years," he said.
Nearly 500 doping samples from the 2006 Winter Olympics in Turin have already been retested. The IOC has not disclosed whether those retests had produced any positive cases.
Five athletes were caught in retests of samples from the 2004 Athens Olympics, including men's shot put winner Yuriy Bilonog of Ukraine.
On a separate issue, Budgett said he is confident that Brazil's national anti-doping agency will comply with World Anti-Doping Agency rules by next week's deadline to prevent Rio's drug-testing laboratory from being ruled ineligible for the Olympics.
The Brazilian agency has until March 18 to meet WADA's guidelines. If it fails, the Rio lab would be declared non-compliant, meaning thousands of doping samples during the games would have to be sent out of Brazil for testing, posing major logistical and financial issues.
Brazilian President Dilma Rousseff is scheduled to sign a decree on March 15 that would bring the agency into compliance.
"We're very hopeful that it finally will be resolved," Budgett said. "The laboratory itself is performing well and really is state-of-the-art. We always have a Plan B. Anything can happen. That's there in case, but I do not expect to be using it."
Budgett said the IOC plans to carry out a "similar number" of tests in Rio as the 5,000 conducted in London. An intelligence unit created by WADA is targeting athletes for testing in the lead-up to the games.
"We're not talking about the numbers any more, we're talking about the quality," Budgett said.