Facing allegations of lax doping standards, international track-and-field officials announced Tuesday that they have retested urine samples from the 2005 and 2007 world championships, finding 28 athletes with positive results.
The International Assn. of Athletics Federations has been storing samples for years in anticipation of newer, better analytical methods.
None of the athletes who came up positive in this latest round of retesting were identified by name. Most are retired, the federation said, and none are scheduled to compete in the upcoming world championships in Beijing.
"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," said Martial Saugy, director of a Swiss lab involved in the testing.
The IAAF has come under scrutiny after German and British media reported that test results leaked from the association's database showed rampant blood doping.
In regards to the latest results, association officials stated: "Should anti-doping rule violations be confirmed against these athletes, the IAAF will correct the record books and reallocate medals as necessary."