As speculation mounts over how Australian swimmer Shayna Jack came into contact with a banned substance, her manager says one possibility may be something she ate and her diet was now being examined.

On Saturday Jack revealed she failed a drug test, forcing her to withdraw from the national squad before the world championships in South Korea.

The Queensland swimmer has said she did not know how the banned substance entered her body, and that it can be found in contaminated supplements.

But this morning Mr Stoneman told reporters Jack did not consume the banned substance through a supplement pill or tablet.

“It could be meat, it could be mushrooms, it could anything. It could be something in a bottle,” Mr Stoneman said.

“There are so many different ways that things can get into your system.

“This isn’t about ducking and weaving about what that might be. We just don’t know.”

Jack’s manager, Philip Stoneman, is adamant the swimmer is innocent. Photo: ABC

Mr Stoneman said Jack will be looking back through the food she ate at the time.

“It’s a bit of jigsaw puzzle as to how this has come into her system. It might be meat but we don’t know, it’s too early to speculate.”

Meanwhile, Swimming Australia (SA) is standing by Jack for being “open and honest”.

The 20-year-old was notified by the Australian Sports Anti-Doping Authority (ASADA) that she failed an out-of-competition drug test in late June.

But SA chief executive Leigh Russell told the ABC on Monday Jack’s situation was “quite different” from that of China’s swimmer Sun Yang, who competed after being cleared of wrongdoing following a random drug test last September.

The World Anti-Doping Agency is appealing that decision.

Ms Russell said SA would be providing support to Jack while ASADA continues its investigations.

“My understanding from Shayna is she doesn’t know how she’s come into contact with the drug,” Ms Russell said.

“She’s trying to find a reason for this substance in her body. Quite rightly she’s asking the question about perhaps what might she have ingested that is contaminated.”

Ms Russell denied there was a double standard, after SA backed Mack Horton’s protest against Yang.

“I think the two are quite different actually. Mack’s protest was about an athlete who is going through a process that was still able to complete at the world championships.

“Our process in Australia is simply that once we have been notified that an athlete has had an adverse test finding, our job is then to remove them immediately from the team environment so they’re not able to compete.”

Shayna Jack says she had never heard of Ligandrol before testing positive to the banned substance. Photo: AAP

Federal Sport Minister Richard Colbeck described the incident as “embarrassing”.

“We want to see clean sport, that’s a very, very clear perspective of the Australian Government, I think the Australian community wants to see clean sport,” Mr Colbeck said.

“So we are all concerned that we have this particular event at this point in time, it is embarrassing.

“Obviously we’ve got a process to go through now to see how it all plays out. But it doesn’t really matter whether it’s at a global level or whether it’s at a local or interstate level, we want sport to be clean, we want athletes to be able to compete against each other on a real basis without any involvement of enhancements.”

Assistant Professor for Sports Management and a lawyer with the University of Canberra, Catherine Ordway, said the onus was on athletes to test any supplements they may have taken.

“These contaminated supplement type cases are very tricky to prove because it’s a very strict liability situation,” she said.

“Which means if there’s a prohibited substance in your sample which is this case, then the onus is on the athlete to try to get their supplements tested in a laboratory and try to demonstrate that they didn’t intentionally put it into their body.”

Ms Ordway said it’s not unusual for supplements to get contaminated.

“That’s why ASADA and body like that put out warnings all the time and do a lot of education with the athletes, particularly elite level ones athletes like Shayna saying don’t take supplements.

SA initially claimed Jack had left the team for “personal reasons” but two weeks later the swimmer herself revealed on social media she had been forced to withdraw over the test failure.

SA came under fire for its handling of the result, and was accused of trying to cover up the test result.

But Ms Russell said on Monday they had to support the process outlined in their contract agreement with ASADA, which prevents SA from disclosing details.

Jack has vowed to clear her name after it was revealed she tested positive for the banned substance Ligandrol — a drug used to aid muscle growth and treat osteoporosis.