The family of a woman in a critical condition after being hit by a Melbourne roller-coaster suffered an unthinkable second tragedy in just a few months.

Shylah Rodden, 26, is in a critical condition after she walked onto a section of the 350m-long track at the Royal Melbourne Show shortly before 6pm on Sunday and was struck by a carriage.

She suffered facial injuries and was transported to hospital on Sunday night. She remains in a critical condition on Monday afternoon.

According to Nine News, Rodden was struck by the Rebel Coaster roller-coaster after trying to retrieve a phone, was lifted into the air and "fell from around nine metres high".

There had been mixed reports about exactly what happened to Rodden. Some witnesses claimed they saw Rodden fall from the ride while others said she walked onto the tracks.

The tragedy comes less than two months after the Rodden family lost Shylah's brother Jason.

In a post on social media, Shylah wrote that her "world came crashing down".

Fairground workers work on the rollercoaster ride after a woman was injured, reportedly attempting to retrieve her mobile phone from under the tracks. Photo / Seven News

"Dad sat me down and told me that my brother had passed away," she wrote on July 27.

"He wasn't just my big brother, he was my best friend, my everything, the person I looked up to and inspired to be like.

"He taught me so much in life, he showed me the difference between right and wrong and he was never afraid to tell me how he really feels.

"It doesn't feel real, I keep thinking you'll call me back."

Rodden's father Alan Rodden is now facing the prospect of losing another child.

Rodden suffered horrorific injuries. Photo / Supplied

Speaking to media on Monday, he said he was still not certain what to believe about the incident that has left his daughter in a critical condition.

"There are a lot of stories going around and I don't know which one is true and if someone is covering their tracks," he told the Daily Mail.

He said his daughter suffered "horrific" injuries and was fighting for her life.

"The injuries are horrific. Horrific. She's brain-damaged. It's pelvic, her arms, legs, back, neck - there's hardly a thing that's not broken," he said.

"I just can't work out how the hell so much damage has been done. Even the doctors have said they haven't seen anything as bad as this for a long time."

As WorkSafe investigates the incident, the CEO of the Melbourne Royal Show is refusing to speculate about the events that led to the young woman's injuries.

Speaking to ABC Mornings host Virginia Trioli on Monday, CEO Brad Jenkins would not say whether there was a fence around the ride or how high that fence was.

"I can't comment specifically on that particular ride," he said. "There [are] operators down at each of the rides."

But a video published on YouTube in 2021 from aboard the ride when it was at the Sydney Royal Easter Show shows a fence around the ride appearing to be no higher than 1.5m.

A video shows fence height on the Rebel Coaster when it was in Sydney last year.

Jenkins said it appears the young woman had "gone to recover her phone" when she was hit. He said he hoped the incident would not deter others from going on the ride for the remainder of the show.

"From all reports she's gone to recover her phone. It's not a malfunction or whatever," he said.

He would not say exactly how she got on to the tracks.

"We don't (know how she got access to the tracks)," he said.

"That's a subject for WorkSafe and police. That's part of the investigation. I wouldn't want to comment on that until the investigation goes through the process."

Asked if any Melbourne Royal Show staff witnessed the incident, he said: "Not our staff witnessing that.

"There'll be obviously a number of witnesses close by, it was an absolute sell-out crowd. The site was very busy."

Jenkins said the operator of the ride was "devastated".

"Carnival operators are very close knit. The show's about trying to put smiles on people's faces."

The Rebel Coaster is described online as "more than 350 metres of exhilarating track".

"You're in for a speedy, action packed ride including two 11-metre drops and a gravity defying giant loop," a description reads.

"Plus zoom through a vortex and zig zag all protected by a high-class safety system."

A stall owner at the show on Sunday told the Herald Sun she heard the roller-coaster stop abruptly as people screamed.

"The screaming was so loud. I think everyone must have been really scared," she said.

"The ride went up like normal, then there were screams, then it stopped and stayed that way for ages."

A Victoria Police statement on Sunday night said the woman was found injured on the ground.

"Police are currently on scene at the Melbourne Royal Show following reports a young woman has been injured," Victoria Police said in a statement.

"Officers are working to establish the circumstances surrounding the incident and a crime scene has been established.

"It appears at this early stage the woman, believed to be aged in her 20s, may have walked on and entered the track to try to retrieve a dropped phone before she was hit by a roller-coaster carriage, about 5.45pm.

"Sadly the woman was then found injured on the ground. Detectives from the Yarra Crime Investigation Unit are attending the scene and will work with WorkSafe to establish the circumstances surrounding the incident."

- Rohan Smith, news.com.au