Dreamworld will remain closed on Wednesday while police examine how four people were killed on a 30-year-old water raft ride at the Gold Coast theme park.
Brother and sister Luke Dorsett, 35, and Kate Goodchild, 32, Canberra man, and Mr Dorsett's partner, Roozi Araghi, 38, and 42-year-old New Zealand woman Cindy Low, died in the catastrophic accident.
The four were victims of a conveyor belt malfunction at the Gold Coast park when their raft flipped on the Thunder River Rapids ride on Tuesday afternoon.
Two were thrown clear of the ride while the other two were stuck in the ride itself.
Two young children who survived Dreamworld's horrific raft ride accident will have the theme park's "full support into the future", chief executive Craig Davidson says.
A 10-year-old boy and a 12-year-old girl were with their mothers - Cindy Low and Kate Goodchild - on the Thunder River Rapids ride when a malfunction caused their raft to flip on Tuesday afternoon.
Queensland Police have appealed for anyone who was on the Thunder River Rapids ride yesterday and anyone with mobile phone footage of the incident to come forward.
Police have not confirmed if the children are related to the two men and two women who died.
The 12-year-old girl is believed to be Ms Goodchild's eldest daughter.
Craig Davidson joined a group of staff to lay a wreath near the Gold Coast park's entrance on Wednesday as the ride remained a crime scene.
He said the team's immediate focus was on the families and friends of the victims.
"I also want to specifically acknowledge the impact of the event on the two children who were involved in this tragedy," he said.
"These children will have our full support into the future."
Queensland Police Assistant Commissioner Brian Codd told reporters the incident had happened at the end of the ride when the raft, or flume, containing the victims crashed into another raft and flipped.
"We know that an occurrence has seen that particular flume be turned over and flipped, resulting in it falling back on top of those persons and those persons being variously caught in machinery - and I don't want to go into too much graphic detail," he said.
He said the children's survival, given what they viewed on CCTV footage of the accident, was miraculous.
"I guess the fortunate thing here is that the two children managed to escape that disaster and, unfortunately, the four adults did not."
He said it was a "miracle" the two children had managed to survive the crash.
Assistant Commissioner Codd said police would conduct a thorough investigation with the Coroner that would take as long as it needed to take.
"We have specialist engineers that will be attending today and will be examining certain componentry that goes with that ride," he said.
"There will be a broad range of things examined - policies, procedures, maintenance schedules - ... the make-up of the whole ride itself in terms of compliance.
"We owe it to the deceased and their families, we owe it to the community of Queensland, to get to the bottom of what caused this, to hold accountable any person that needs to be held accountable for this occurring, if that is the case, but most particularly ensuring that this can never happen again."
The mother of Mr Dorsett and Ms Goodchild has told the Courier Mail the accident has devastated her family.
"I have three children and have lost two of them today - my whole family has been wiped out," Kim Dorsett told the Courier Mail.
Ms Goodchild had two daughters, aged eight months and 12 years. Ms Dorsett said the oldest girl was blaming herself.
"She has had a truly terrible day, she is going through unimaginable pain at the moment," Ms Dorsett said.
"I'm at a loss as to how to deal with this now - I woke up this morning with three children and tomorrow I am only going to have one left."
Canberra-based Ms Dorsett and her family were holidaying on the Gold Coast and had extended their stay by a few days.
A team of 30 detectives is involved in the investigation amid union claims it raised grave concerns about safety at the park 18 months ago, and that owner Ardent Leisure fought efforts to obtain relevant information.
Both Mr Dorsett and Ms Goodchild worked for the Department of Human Services in Canberra, and department secretary Kathryn Campbell said the two had been valued employees.
"Kate and Luke were well-liked and respected by their colleagues and will be greatly missed," Ms Campbell said.
The Australian Workers Union, which represents Dreamworld staff, says it took safety concerns to Ardent as far back as April 2015, and even submitted right- to-information requests with the division of Workplace Health and Safety.
But Ardent Leisure opposed them, AWU Queensland Secretary Ben Swan has told ABC radio.
"We have had concerns about maintenance and operations regimes," Mr Swan said on Wednesday, declining to provide details and adding that he could not speak about the safety of the ride in question.
"What I can say is that it's now a matter of public record, because we put right to information requests into the division of Workplace Health and Safety that we had concerns."
Meanwhile, there have been claims the ride was due to have been closed for maintenance on Tuesday.
So-called hacktivist group Anonymous has posted what it claims is proof a reference to the planned maintenance closure was removed from Dreamworld's website.
Several parkgoers claimed the ride had broken down at least twice earlier in the day.
Comment has sought from Ardent.
'It all happened so fast'
Dreamworld visitors described the chaos after the accident at 2.20pm.
"It all happened so fast. One minute we were just about to get on the ride and the next there was this little girl screaming and we were just trying to comfort her," Lia Capes told the Courier Mail.
Several parkgoers claimed the ride had broken down at least twice earlier in the day and police said those claims would form part of the investigation.
The deaths had an immediate financial impact on the park's owners Ardent Leisure, as it shares fell 7.8 per cent on news of the tragedy.
Queensland Ambulance senior operating officer Gavin Fuller said on Tuesday the victims suffered fatal injuries and couldn't be revived despite several crews attending the scene.
Thousands of patrons left the park in shock following the tragedy.
A coronial investigation into the cause of the accident and the deaths is underway, with workplace health and safety officers and police forensic crash investigators also involved.
The company released a statement on Tuesday night saying "the entire Dreamworld team is devastated and shocked by this incident".
Dreamworld chief executive Craig Davidson said their thoughts were with the families and loved ones of those killed.
"Dreamworld is absolutely committed to fully supporting the authorities investigating the incident so we can find out exactly what has occurred," he said.
The Thunder River Rapids ride is currently Australia's only river rapids ride and opened in December 1986.
Dreamworld's Rocky Hollow Log Ride was shut down in April this year when a man fell from the ride and nearly drowned.
Assistant Commissioner Codd was emotional as he spoke of the impact the incident had had on witnesses, including the two children who survived the crash, and first responders.
"Obviously, at the initial scene, absolutely traumatic for these children, and it will continue to be," he said.
"I'm advised that they're being provided care from their family, but there's also offers of care and support from both internal QPS services, our chaplaincy, and also through Lifeline where counsellors are also being provided by government sources to strengthen up their capacity to support not only those kids but many members of the public - witness, child or adult - that I guess the reality will start to hit them about that tragedy, those services will be available and they're a very important part of what we need to do here."
He would not comment on reports some of the victims' family members witnessed the crash.
The Gold Coast is safe, Premier Palaszczuk
Queensland Premier Annastacia Palaszczuk has vowed to ensure the Gold Coast recovers from the devastating Dreamworld accident that has left four dead.
"There will be a thorough investigation by the police and the coroner. We need to ensure that this never happens again," she told the Seven Network on Wednesday.
But she said the immediate priority was to ensure the children and family of the victims, staff at Dreamworld and emergency services who attended Tuesday's horror accident are cared for.
More counsellors and support staff will be sent to help staff and others deal with the aftermath of the fatal accident.
Gold Coast Mayor Tom Tate earlier told Nine that the council would help the family of Dreamworld.
"I mean, they're used to giving fun and joy to people and all of a sudden, the memories this memory will leave behind is the most horrific," Gold Coast Mayor Tom Tate told Nine on Wednesday.
"We're going to have to help the family of Dreamworld."
Ms Palaszczuk and Mr Tate said the accident had hit a lot of locals and Australians hard and have vowed to ensure the tragedy is thoroughly investigated, but said the Gold Coast was safe.
"We will leave no stone unturned. There will be a thorough investigation by the police and the coroner. We need to ensure that this never happens again," Ms Palaszczuk said.
More than 30 police investigators were at Dreamworld again on Wednesday.
Mr Tate said the theme parks were vital to the Gold Coast economy.
"It's very important for us ... [to] help support the theme parks and get them back to the point where people have the confidence to come and live and have their wonderful memories again."
Ms Palaszczuk has urged anyone who needs help to contact Lifeline.
Lifeline on 13 11 14.