THE teammates of the Australian swimmer dropped from the national squad and sent home after testing positive to a banned substance have arrived back in Brisbane today.

Shayna Jack failed a drug test and was withdrawn from the team ahead of the world Championships in South Korea after testing positive for prohibited substance Ligandrol.

Speaking to media as he arrived in Brisbane this morning, Jack's coach Dean Boxall admitted, "I don't know what's happened."

Yet he said the scandal hasn't affected the morale of the team.

"The team has been so united... and the way that we performed was remarkable. I don't think this has overshadowed the group," Boxall said.

Jack has vehemently denied intentionally taking the muscle builder substance which is known to increase lean muscle mass and improve athletic performance.

Over the weekend, she took to social media saying she was feeling "pain and vulnerability" after her failed drug test was made public.

"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," she said on Instagram.

"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."

Boxall said he has kept constant contact with Jack since the revelations.

"She's going through some tough times. I'm feeling very sorry for the girl... she's a 20-year-old girl," he said.

"And she doesn't have the answer yet."

The coach said he is about to meet up with Jack today and discuss next steps.

"I don't know too much what's going on because we've just had a competition. But we're going to fight. We've got a very good lawyer," he said.

He said he "believes" in Shayna and said she will fight it.

"I believe in Shayna so we just have to go through the process," he said.

"She's a remarkable athlete and great girl and she'll fight it and I happily dream she's still alive and kicking."

It comes just one week after her teammate Mack Horton refused to share the podium with Chinese swimmer Sun Yang in a silent protest against doping in the sport.