The International Association of Athletics Federations has confirmed that its retesting strategy has found 32 "adverse findings" in the samples of 28 athletes that competed at the World Athletics Championships in 2005 and 2007.
Beginning in April 2015 and following the World Anti-Doping Code's provision to extend from eight to 10 years the period during which samples can be tested, the IAAF made a second reanalysis of the Helsinki 05 and Osaka 07 tests, which has brought about the revelation.
According to the governing body, many of the 28 athletes in question have since retired, but they cannot be named for legal reasons.
However, the IAAF has confirmed those that are still active in the sport will not be permitted to participate at this month's Championships in Beijing.
The news has come after seven British athletes, including Mo Farah, agreed to have the results of their blood tests made public.
