American sprinter Marion Jones could face a two-year ban from athletics if a B sample confirms her initial failed drugs test.
Jones was a surprise withdrawal from Friday's Weltklasse meeting in Zurich.
Reports in the United States claim the 30-year-old has tested positive for EPO (erythropoietin), a blood-boosting hormone.
Jones has already stated her innocence through her lawyer.
However Pierre Weiss, general secretary of the International Association of Athletics Federations, confirmed the world governing body were awaiting results of a B test.
Weiss told the BBC: 'For us, the situation is clear, an athlete is only positive once an A sample has tested positive and the contra-analysis of the B sample confirms this.
'This is not the situation at the moment.
'We are waiting reports regarding this case, which is why we cannot speak more.
'We have spoken with USTAF (United States Track and Field) but we are still waiting for what the contra-analysis tells us about this case.'
Jones has been dogged by allegations of drug taking since winning five Olympic medals at the 2000 Sydney Olympics, particularly during the the Bay Area Laboratory Co-operative (BALCO) drugs scandal.
However she has never faced charges and has repeatedly stressed she is a clean athlete.
Jones withdrew from Friday's Golden League meeting, citing 'personal reasons' for having to return home.
Although that explanation would usually suffice in the case of an athlete withdrawing from competition, Weiss believes Jones could have been more open.
'We would have preferred that she stated what those personal reasons are. It would have made things more clear for the news media, the general public and the IAAF,' he said.
Jones, who won three gold medals in Sydney, may have previously been tainted by association.
Her former husband, shot putter CJ Hunter, retired after being found guilty of a drug offence in 2000, then Tim Montgomery, a former partner with whom she has a child, was also suspended last December.
Montgomery was involved in the BALCO investigation and apart from receiving a two-year ban, was also stripped of his world 100m record set in September 2003.
Widely regarded as the most accomplished sprinter since the late Florence Griffith Joyner, former basketball player Jones won both the 100metres and 200m in Sydney - plus a relay gold - and is also a double former world champion at the shorter sprint.
She was investigated by the United States Anti-Doping Agency when the whistle was blown about the designer drug THG, which resulted in Montgomery and many US leading athletes plus British sprinter Dwain Chambers suspended.
However there was no evidence of Jones having cheated and there has never been confirmation of a failed drug test.
The Washington Post, citing an unnamed source, reported on Saturday that an 'A' sample from Jones produced a positive EPO result following a test at the USA Track and Field Championships held from June 22-25.
