Australian swimmer Shayna Jack claims she was forced to leave the national team before the world swimming championships in South Korea because of "allegations of having a prohibited substance in my system".
It has been reported Jack has tested positive for a banned substance, although Swimming Australia has yet to confirm if this is the case.
But Jack took to Instagram to explain why she left the Australian squad ahead of the world titles.
"It is with great sadness and heartache that I had to leave due to allegations of having a prohibited substance in my system," Jack wrote.
"I did NOT take this substance knowingly. Swimming has been my passion since I was 10 years old and I would never intentionally take a banned substance that would disrespect my sport and jeopardise my career.
"Now there is an ongoing investigation and my team and I are doing everything we can to find out when and how this substance has come into contact with my body.
"I would appreciate if you respect my privacy as this is very hard for me to cope with."
Jack had posted on Instagram earlier in the month her withdrawal was because of "personal reasons".
The 20-year-old was a member of Australia's 4x100m freestyle relay team that set a world record at last year's Commonwealth Games on the Gold Coast.
She also won two silver and two bronze medals in relays at the 2017 world championships in Budapest.
Jack's revelation comes at a time when Australia has been front and centre at the world championships amid the ongoing campaign to clean up swimming and improve anti-doping procedures.
Australian swimmer Mack Horton sparked controversy when he refused to acknowledge Sun Yang after the Chinese star relegated him to 400 metres freestyle silver in Gwangju on Sunday.
Sun, who served a doping ban in 2014, faces a lifetime suspension if found guilty of charges that he smashed a vial of his blood with a hammer in a clash with testers at his home last year.
The allegations of doping rule violations could result in a ban from the 2020 Tokyo Olympics and he has requested a public trial at the Court of Arbitration for Sport (CAS) in September to defend himself.
Horton refused to share the medal podium with Sun, choosing to stand behind it, while also declining to be photographed with the gold medallist.
Swimmers quickly threw their support behind Horton, who was angry that Sun had been allowed to compete ahead of the CAS hearing.
