Small amounts of the banned substance clenbuterol have been retroactively found in the samples of Jamaican sprinters at the 2008 Olympic Games, according to a report on Sunday.
German broadcaster ARD claims the International Olympic Committee (IOC) learnt of the discovery late last year, but no action has been taken as the levels detected by testing using updated techniques are so small.
ARD has not specified which Jamaican athletes' samples are affected from the Beijing Games, where superstar Usain Bolt won three gold medals, but said other athletes from other countries also failed retroactive testing.
The ARD report quotes Olivier Niggli, director of the World Anti-Doping Agency (WADA), saying: "I am aware of the fact that there are Jamaican cases with very low levels of clenbuterol.
"If the amounts found are relatively low compared to direct intake of the substance, WADA accepts that such cases are not announced."
Jamaica originally won five golds in the sprint events at the 2008 Games.
However, the 4x100m men's relay team had to give their golds back in January after Bolt's team-mate Nesta Carter retrospectively tested positive for the stimulant methylhexanamine.
An IOC statement has confirmed the ARD report that some samples taken at Beijing 2008 contained clenbuterol.
"During the re-analysis of the stored urine samples from the Olympic Games Beijing 2008, the laboratory found in a number of cases of athletes from a number of countries and from a number of different sports, very low levels of clenbuterol," said the IOC in a statement.
"All of the values were below 1ng/ml and therefore in the range of potential meat contamination cases.
"To protect these innocent athletes, we cannot reveal any more details about them and we expect that these athletes’ rights are also respected by the media."
Clenbuterol is the performance-enhancing substance which saw Spanish cyclist Alberto Contador stripped of his 2010 Tour de France title and banned for two years after testing positive during that year's race.