SYDNEY (AP) — IOC vice president John Coates says the most recent positive doping results of backdated tests from athletes competing at the 2008 Beijing Olympics proves "if we don't get you at the Games, we will get you later."

In a major doping crackdown, 31 athletes in six sports could be barred from competing at the Rio de Janeiro Olympics in August after they were caught in retesting of doping samples from 2008.

The International Olympic Committee has opened disciplinary proceedings against the athletes from 12 countries who competed in Beijing and were planning to take part in Rio. The names and countries have not been published.

"I don't know where these athletes come from, or what the sports are," Coates, who is also president of the Australian Olympic Committee, said in Sydney on Wednesday ahead of a team dinner. "This was a very targeted test, and what pleases the IOC with our zero-tolerance policy is that the testing is catching up.

"My mantra has always been 'if we don't get you at the Games, we'll get you later.' And that's been validated."

The retesting of Beijing samples is a first step for the IOC, which will undertake a similar procedure for tests from London 2012 and the Sochi Winter Olympics of 2014.

"In a week, we expect to have results of the retest from about 250 London samples," Coates said. "In addition to the retested samples — we obviously targeted those who are still competing (first) — we obviously have to go back and look at the other samples to ensure nobody has missed out on a medal, and a medal hasn't been taken by a cheat."

Coates also said he was yet to receive confirmation that former Australian swim coach Scott Volkers — who has faced sexual abuse charges of female swimmers in the 1980s, but who has never been found guilty — had been banned from taking a role with the Brazil team for Rio. The AOC had earlier warned the Brazilian federation against the appointment.

"I've read the reports in the Brazilian media, I haven't had it confirmed but that appears to be the case," Coates said.