Twenty-eight athletes who competed at the 2005 and 2007 World Championships have returned “adverse findings” from retested samples, the International Association of Athletics Federations (IAAF) has said.
According to the world governing body, a large majority of the athletes are retired with “very few” still active.
“The IAAF is provisionally suspending them,” it said in a statement.
There are no British athletes among those with adverse doping samples.
The IAAF, which has been criticised after leaked blood test data was obtained by the Sunday Times and German broadcaster ARD/WDR, added that none of the athletes concerned would be competing at the 2015 World Championships in Beijing, which get under way on 22 August.
None of the 28 can be named yet “due to the legal process”.
The 2005 World Championships took place in Helsinki, Finland, with Japanese city Osaka hosting the event two years later. If violations are confirmed the IAAF will correct the record books and re-allocate medals as necessary.
Earlier this month, The Sunday Times said the results of 12,000 blood tests from 5,000 athletes between 2001 and 2012 showed an “extraordinary extent of cheating” by athletes at the world’s biggest events.
However, the IAAF responded by describing allegations of widespread doping in athletics as “sensationalist and confusing”.
The World Anti-Doping Agency’s independent commission is investigating the claims.

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