0858 GMT January 23, 2020
The 20-year-old, part of Australia's 4x100m freestyle team that set a world record last year, is facing a lengthy ban after Ligandrol, which helps build muscle mass, was detected in an out of competition test in late June, AFP reported.
It proved hugely embarrassing for Australian swimming, with the result emerging just days after Olympic champion Mack Horton's high-profile protest against Chinese rival Sun Yang over alleged testing violations at the world championships in South Korea.
Jack has denied knowingly taking the drug and met with officials from the Australian Sports Anti-Doping Authority (ASADA) in Brisbane for a briefing on the test results.
"I am not going to stop until I prove my innocence, and I am going to fight to get myself back in the pool because that's my dream and I'm never going to let that go," she told reporters afterward.
Asked where she thought the substance came from and how it got in her system, she replied, "It's still an ongoing investigation so we can't clear that one up at the moment.
"We're still looking into it and we're not going to leave any stone unturned."
Her manager Phil Stoneman insisted this week Jack did not ingest the drug via supplement tablets and they were examining her diet.
"It could be meat, it could be mushrooms, it could be anything. It could be something in a bottle," he told national broadcaster ABC.
"It's a bit of jigsaw puzzle as to how this has come into her system."
After Horton refused to share a podium with Sun at the world championships, Jack's positive test saw Australian swimming accused by Chinese state media of being hypocritical in its crusade against doping.
Sun was cleared of wrongdoing after being accused of smashing vials of blood following a test last year, although the decision is the subject of a World Anti-Doping Agency (WADA) appeal.
Jack's lawyer Paul Horvath said in a statement Friday the next step in the process was "correspondence from ASADA in about four to six weeks."
"Shayna has handled herself very well today through a long and challenging process, especially for a 20-year-old," he added.