Olympic gold medal swimmer Kylie Palmer was cleared 18 months ago of the alleged doping violation that now threatens to derail her career.
Palmer has withdrawn from the Australian team for next month's world championships in Russia after accepting a provisional suspension, following FINA's notification in April she had tested positive to a minute amount of a prohibited substance.
The test was taken at the 2013 world titles in Barcelona, where she won a 4x200m freestyle relay silver medal with Bronte Barratt, Brittany Elmslie and Alicia Coutts.
The banned drug found in her system was the diuretic furosemide, according to News Corp.
Questions circled in the swimming world on Thursday about why nearly two years had passed before FINA eventually notified and charged the 25-year-old Queensland middle-distance star.
Late on Thursday night, world swimming's governing body revealed they had investigated and cleared Palmer of a doping breach back in January 2014, but were forced to issue a belated violation after the World Anti-Doping Agency (WADA) appealed to the Court of Arbitration for Sport (CAS) this February.
FINA said it decided not to pursue the matter because the levels of the substance detected in Palmer's system on July 31 in 2013 were so low.
Other tests conducted on July 25 and August 1 - one day after the low finding - were both negative, as were an additional two target tests subsequently requested by FINA.
The 20-month delay renders the case extremely problematic for Palmer, who categorically denies knowingly taking any prohibited substance but conceded proving she unknowingly ingested it would be an "almost impossible" task.
Swimming Australia CEO Mark Anderson voiced his concern directly to FINA.
"This event did occur back in 2013, so we are all very mindful of the difficulties that creates for all parties," Anderson said on Thursday.
Palmer, who won gold in the 4x200m freestyle relay at the 2008 Beijing Olympics and silver in London 2012, had her sights set on competing in a third and perhaps final Games in Rio next year.
But that dream is in the balance, given furosemide carries a maximum two-year suspension under FINA Doping Control Rules.
That can be decreased or completely removed if Palmer can demonstrate how the drug entered her body and therefore prove it wasn't intended to enhance performance or mask another drug that does.
Diuretics are banned because of their capacity to mask other substances.
Any suspension would still see Palmer's entire 2013 relay team disqualified and stripped of their medals under FINA rules.
Palmer's legal team have started preparing her defence, though a tribunal hearing date is yet to be set.
