LONDON - The IAAF has initiated disciplinary action against 28 athletes after they retested samples from the 2005 and 2007 world championships with new technology that can uncover previously undetectable substances and found 32 adverse doping cases.

Eastern Europeans, including Russians, make up a large number of the 28, sources familiar with the testing told Reuters on Tuesday.

They were not aware of any Americans on the list and the BBC reported there were no British athletes.

The world athletics governing body said it could not yet name the 28 or even their nationalities, "due to the legal process".

"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 International Association of Athletics Federations (IAAF) said.

"The IAAF is provisionally suspending them and can confirm that none of the athletes concerned will be competing (at the world championships) in Beijing."

The 2015 world championships start in the Chinese capital on Aug. 22.

The tests were the second for samples from the 2005 world championships in Helsinki.

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.

Officials at the World Anti-Doping Agency (WADA) would not comment on the cases, saying they would await the conclusion of the testing process.

If violations are confirmed, the IAAF said it would correct the record books for the 2005 and 2007 world championships, which were held in Osaka, and re-allocate medals as necessary.

"The latest scientific breakthroughs in anti-doping technology and analysis have been employed in the re-analysis of these samples to allow us to find previously undetectable substances," Martial Saugy, director of the Swiss Laboratory for Doping Analyses in Lausanne, said in a statement.

Since 2005, the IAAF has stored athletes' samples from previous championships at the laboratory for future re-analysis.

The latest retesting began in April, "well before the most recent allegations made against the IAAF by the ARD and The Sunday Times", the IAAF said.

The German broadcaster and British newspaper had criticised the IAAF, saying it had failed to investigate hundreds of what they called "suspicious" drug tests between 2001 and 2012.

"The findings reconfirm, yet again, the commitment of the IAAF to target and uncover all cheating in the sport, no matter how long it takes," the governing body said.

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.

To date, nine athletes have been sanctioned after retests of samples from various world championships.

"The IAAF does not shy away from the fact that some athletes continue to cheat and defraud their fellow competitors," the federation said in its statement.

"But we will do everything in our power, and use every tool available to protect those clean athletes who form the large majority of our sport."