Jack said she did not "intentionally take this substance".
Australian swimmer Shayna Jack, who was forced to withdraw from the World Championships in South Korea after failing a drug test, has revealed she tested positive for the substance Ligandrol.
Swimming Australia has refuted allegations it embarked on a cover-up, despite failing to publicise the swimmer's situation when it knew the real reason for her absence.
The Australian Sports Anti-Doping Authority found an adverse result in an out-of-competition test on 26 June.
Details of the substance in question have not been disclosed.
She was sent home to Australia, suspended from the team and banned from competing at the 2019 world championships in South Korea while the Asada investigation was under way.
In a lengthy statement on Instagram Sunday Jack, 20, also revealed she was told on July 19 her B sample had tested positive for the same substance.
The four-time World Championship medallist added: "It is far with grand unhappiness and heartache that I needed to scramble away ensuing from allegations of getting a prohibited substance in my device".
"Now there is an ongoing investigation and my group and I are doing all the pieces we are in a position to to search out out when and the design this substance has come into contact with my body".
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Olympian Raelene Boyle has criticised the rules around the Shayna Jack drug scandal after Swimming Australia said they were forbidden from coming clean.
His stoush with China's Sun Yang has been ongoing since Rio, where Horton called Sun a "drug cheat', and continued into Gwangju with the 23-year-old Australian refusing to take the podium or shake his hand after the men's 400m freestyle".
"I think that's a conversation that we'd be interested in having at a later stage", she said. She's [Jack] not here [in Gwangju] and it shows that the Australian system works. "We have consistently supported a zero tolerance approach to doping and have been strong supporters of a rigorous and consistent approach to drug testing both here and overseas", CEO Leigh Russell said.
Sun served a three-month doping ban in 2014 and is facing a hearing with the Court of Arbitration for Sport (CAS) in September to determine if his original not-guilty verdict will be overturned in regards to smashing vials of his own blood when visited by drug testers past year.
"Officials initially failed to elaborate on the circumstances behind her exit", said The Australian.
"I had absolutely no knowledge of this before tonight", she said after her 50 meters freestyle heats.
Many of Sun's rivals believe he should not be competing, with the 27-year-old due to face a Court of Arbitration for Sport hearing in September over a separate doping offence.