Aussie swimmer Shayna Jack has reportedly tested positive for a banned substance.

On July 14, Jack announced she had withdrawn from the World Swimming Championships in South Korea due to “personal reasons.”

According to 9News, the 100-metre freestyler failed a routine drug test. However, it’s unclear what Jack tested positive for.

On Instagram on Saturday evening, Jack confirmed the positive result but said she did “not take this substance knowingly.”

“It is with great sadness and heartache that I had to leave due to allegations of having a prohibited substance in my system.

“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 body.

“I would appreciate if you respect my privacy as this is very hard for me to cope with,” Jack concluded.

View this post on Instagram

They say a picture is worth a thousand words, in this case a picture can not describe the amount of pain and vulnerability I am feeling right now. It is with great sadness and heartache that I had to leave due to allegations of having a prohibited substance in my system. 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

A post shared by Shayna Jack (@shayna_jack) on

The news comes after a week of anti-doping podium protests at the world championships against controversial swimmer Sun Yang of China, led by Australia’s Mack Horton. 

Image: AAP / DARREN ENGLAND