The athletics world has been rocked on by "wild" doping allegations involving hundreds of suspect blood samples.
International Olympic Committee members and sports federation chiefs woke up to the news that IAAF test data had been leaked to news organisations and that it allegedly showed suspect samples from athletes, including Olympic and world championship medallists.
Around 146 medals, including 55 golds
, at the Olympics and World Championships between 2001 and 2012 have been won by athletes who returned suspicious tests.
Over 800 athletes'
blood tests are 'highly suggestive of doping or at the very least abnormal', according to experts.
At London 2012, ten medals
were awarded to athletes with 'dubious' test results.
More than 80% of medals won by Russian athletes are those whose results are 'suspicious'.
Britain's Sunday Times newspaper and German broadcaster ARD/WDR say they were given access to the results of over 12,000 blood tests provided by more than 5,000 athletes over 11 years in a case that could plunge athletics into a new doping crisis.
The tests showed more than 800 athletes had given blood samples that were "highly suggestive" of doping or "abnormal", reported the BBC, who added they had also seen the documents.
The news appeared to take the president of the athletics federation (IAAF) Lamine Diack by surprise, and he offered no immediate reaction when contacted by Reuters.
The World Anti-Doping Agency said it was alarmed by the size and extent of the allegations.
"These are wild allegations, wide allegations and we will check them out and have that done with the commission as quickly as possible," WADA chief Craig Reedie told reporters at the IOC Session meeting in Malaysia.
"It was the spread of the allegations that came from previous programmes [that surprised me]. If you look at allegations on blood issues... they are even wider. So that's a concern. But I stress athletes are innocent until proven guilty."
Although abnormal blood tests are not in themselves proof of doping, the release of the data will be an embarrassment to the IAAF just weeks before the world championships in Beijing, where the IAAF will also elected a new president.
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"There will be zero tolerance, this is clear," IAAF Vice President Sergey Bubka said after meeting with WADA's Reedie and Diack, who is stepping down later this month.
"The IAAF is translating the script as it is important to clearly understand the specific allegations.
"We will not go into details now but the IAAF is a very strong leader in the fight against doping. We will not stop the fight. If we need to change rules and regulations we will do it."