(REUTERS) - Jamaican Olympic sprint relay gold medallist Nesta Carter has returned an anti-doping violation for the banned stimulant Methylhexanamine after the re-testing of 454 samples from the 2008 Beijing Games, two sources familiar with the case have told Reuters.
The sources, who spoke on condition of anonymity, said traces of Methylhexanamine were discovered in Carter's "A" sample, part of a batch of 454 from the 2008 Games that the International Olympic Committee (IOC) ordered to be re-tested.
Carter could face sanctions only if his "B" sample also tests positive for the substance.
Reuters has not seen the laboratory results.
Neither Carter, who won gold in the 4x100 metres relay with Jamaican team-mates Usain Bolt, Asafa Powell and Michael Frater in Beijing, nor his agent replied to repeated requests for comment.
Jamaica Olympic Association (JOA) president Michael Fennell declined to comment. Jamaica Athletics Administrative Association president Warren Blake told Reuters his organisation had not been notified of any rule violation.
Methylhexanamine has been on the World Anti-Doping Agency (Wada) Code prohibited list since 2004, although it was reclassified on the 2011 list as a "specified substance".
Wada defines specified substances as those that are more susceptible to a "credible, non-doping explanation".
Sold as a nasal decongestant in the United States until 1983, Methylhexanamine has been used more recently as an ingredient in dietary supplements.
The IOC programme of revisiting samples is aimed at using developments in testing techniques to expose traces of drugs that were undetectable in 2008 or 2012.
Doping cases are usually handled by the relevant national federations and national anti-doping agencies but the IOC has decided that any arising from the re-tests will be dealt with directly by them.
"We want to keep dopers away from the Olympic games in Rio de Janeiro. This is why we are acting swiftly now," IOC president Thomas Bach said last week when announcing the re-testing of 265 samples from the London Olympics.
"I have already appointed a disciplinary commission, which has the full power to take all decisions on behalf of the IOC."
First-leg relay specialist Carter has been a vital member of Jamaica's dominant 4x100m squad, helping the Caribbean island win gold medals at the 2008 and 2012 Olympic Games and the 2011, 2013 and 2015 world championships.
Although his relay team-mates are not accused of doping, it is possible that the IOC could strip them of their gold medals if Carter's B-sample tests positive.