Turning to new technology to uncover previously undetected substances, the IAAF retested samples from the 2005 and 2007 world championships and found 32 adverse doping findings from 28 athletes.
Due to the murky legal situation no names have yet been released about the athletes involved, but disciplinary action has been started.
The news comes after days of public wrangling in the sport following publication of allegations in the Sunday Times and a documentary on German television, which alleged that 800 tests were suspicious out of 12,000 samples tested.
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The IAAF's statement said that "only very few remain active in sport", that most of the athletes have now retired, and that several had already been sanctioned.
The BBC's Dan Roan later claimed that six of the 28 involved are still competing; the IAAF's statement said that those involved have been suspended.
If violations are confirmed the IAAF says it will amend the record books for the 2005 event in Helsinki and the 2007 world championships in Osaka, and re-allocate medals.
According to the statement, the re-testing process had begun before the Sunday Times and ARD allegations.
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Officials at WADA have declined to comment, saying they would await the conclusion of the testing process.
The IAAF took advantage not only of improved testing procedures but also a longer statute of limitations for retesting samples. It was recently extended from eight to 10 years.
"This was one of a number of enhancements made within the 2015 World Anti-Doping Code that we hope will significantly strengthen anti-doping programmes worldwide," WADA said.
It would not name what scientific breakthroughs might have been used in the testing.
"WADA does not disclose when we incorporate new techniques or methodologies in anti-doping, as this can serve to assist those that choose to dope," the agency said.
The tests were the second conducted on samples from the 2005 championships.
The first, in 2012, revealed six adverse findings. Five of the six were medal winners, all representing either Belarus or Russia. Two other athletes, an Indian discus thrower and Ukrainian hammer thrower, tested positive during the championships.
To date, nine athletes have been sanctioned after retests of samples from various world championships.


The IAAF’s long-term storage and retesting strategy concerning IAAF Championships which began in 2005 with the storage of anti-doping samples from that year’s IAAF World Championships in Helsinki has led to disciplinary action being commenced against a further 28 athletes following a second reanalysis.
In 2012, the IAAF conducted a first round of re-analysis of urine samples taken at the Helsinki World Championships which had been proactively stored by the IAAF at the Swiss Laboratory for Doping Analyses (LAD), the WADA-accredited laboratory in Lausanne, in anticipation of new scientific developments. This strategy first revealed six adverse findings from Helsinki which were announced in March 2013 and to date 9 athletes have been sanctioned following re-testing of samples from various world championships.
Beginning in April 2015, using the latest technology available in the field of anti-doping and taking advantage of the new World Anti-Doping Code’s provision extending from 8 to 10 years the period during which samples can be tested, the IAAF made a second reanalysis of Helsinki 2005 and Osaka 2007 samples. This reanalysis has confirmed a further 28 athletes with 32 adverse findings.
Due to the legal process, none of these athletes can be named yet.
A large majority of the 28 are retired, some are athletes who have already been sanctioned, and only very few remain active in sport. The IAAF is provisionally suspending them and can confirm that none of the athletes concerned will be competing in Beijing.
The IAAF embarked on this long-term storage and retesting strategy in 2005 to ensure that clean athletes are ultimately rewarded for their honest efforts in IAAF competitions. The IAAF is committed to use every means at its disposal within the World Anti-Doping Code to root out the cheats, however long it takes.
Martial Saugy, Associate Professor, PhD, Life Sciences, and Director of LAD commented:
“The latest scientific breakthroughs in anti-doping technology and analysis have been employed in the reanalysis of these samples to allow us to find previously undetectable substances. We are at the cutting edge of the fight against doping. In our 10-year partnership with the IAAF we have been using every scientific advance and legal opportunity at our disposal to catch the cheats. The IAAF and the IOC, working in cooperation with the LAD, clearly showed the way 10 years ago and other anti-doping organisations and sport federations, on WADA’s recommendation, are now considering or have started implementing such a retesting policy.”