Two men and two women are dead after an accident on the Thunder River Rapids ride at Dreamworld on Australia's Gold Coast, as visitors to the themepark claim the ride was not working earlier in the day.
The front of the ride's raft is understood to have flipped, trapping two people on the conveyor belt and ejecting two others, Queensland Ambulance acting supervisor Gavin Fuller said at a press conference.
The four people who died were between the ages of 32 and 40, Mr Fuller said.
Emergency services rushed to the popular tourist and family destination shortly after 2pm on Tuesday.
Witnesses said the horrific accident happened as the ride was coming to an end.
'My sister and niece were in the ride, they were so traumatised, there is a woman hanging by her foot, crushed from the ride,' a witness told Gold Coast Bulletin.
Other visitors to the themepark, Kaylah Walker, 25, and her mother Lisa, claimed the Thunder River Rapids ride was not working earlier on Tuesday.
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Two men and two women between the ages of 32 and 40 have died at the Thunder River Rapids ride at Dreamworld on Australia's Gold Coast
Emergency services were called shortly after 2pm on Tuesday after one of the ride's raft is understood to have flipped as it was on the incline
Two of those that died had been trapped beneath the raft on the conveyer belt, and the other two were ejected from the raft as it flipped
'Earlier in the day it had broken down,' Lisa told Sydney Morning Herald.
'It had broken down and we went back a couple of times to this particular ride.
Mr Fuller said the four people killed sustained injuries incompatible with life'.
'One of the rides has sustained some sort of malfunction, causing two people to be ejected, two caught, two males and two females.'
Mr Fuller could not say whether the two people trapped were underwater, and would not elaborate on any of the injuries the four people sustained.
However, witnesses have claimed two of the victims were trapped while the other two fell into the ride's water.
Witness Lia Capes told the ABC she was just about to go on the ride when she saw people running out, crying.
'I was speaking to one of the guys and he said it was the raft or the boat thing in front of him, the whole thing flipped and everyone was screaming,' Ms Capes said.
Dreamworld staff drained water from the ride in an attempt to save the trapped passengers and treated those injured before paramedics arrived.
'One of the rides has sustained some sort of malfunction, causing two people to be ejected, two caught, two males and two females,' the Queensland Ambulance acting superviser said
A coroner will investigate and police have established a crime scene. There will also be a workplace health and safety investigation
CEO of the theme park, Craig Davidson, said at a press conference about 4.45pm the team was 'deeply shocked and saddened by this and our hearts and our thoughts go to the families involved and to their loved ones'.
Police have not identified those killed and would not say whether they were related or if any other relatives were on the ride at the time.
However, a witness told Sky News they saw a young girl who may have been related to the victims crying.
A coroner will investigate and police have established a crime scene. There will also be a workplace health and safety investigation.
Todd Reid, Inspector Regional Duty Officer, would not confirm witness reports that the ride had been faulty earlier in the day.
'Dreamworld is working as quickly as possible to establish the facts around the incident and is working closely with emergency authorities and police to do this,' a Dreamworld spokesperson said.
The park was completely evacuated about 4pm, with hundreds of shocked patrons streaming out.
Dreamworld staff drained the water from the ride in an attempt to save the trapped passengers
Emergency services are pictured at the scene on Tuesday afternoon after two men and two women died
People are seen sitting outside of Dreamworld after it was evacuated following the accident (pictured)
Witnesses said the accident was horrific and happened as the ride was coming to an end
Prime Minister Malcolm Turnbull said he was 'very saddened to learn of the tragic accident'.
'Theme parks are a place for family fun and happiness, not tragedy. This is a very, very, sad, tragic event. Our thoughts and prayers are with the families of those who lost their lives,' Mr Turnbull said in a statement.
'This is a very sad day, and we trust there will be a thorough investigation into the causes of this accident over the days to follow.'
Gold Coast Mayor Tom Tate said it was a 'very sad day for our city' in a statement.
'Our thoughts are with the families of those affected – and the emergency staff in attendance.'
A similar Dreamworld ride called Rocky Hollow Log Ride was shut down in April for a weekend after a man almost drowned, according to The Courier Mail.
A Queensland Ambulance spokeswoman said at the time the man swallowed water after he fell from the ride.
Shocked US Olympic gold medalist Matthew Centrowitz said he had been on the ride just a few minutes before the accident.
Dreamworld has come under scrutiny previously when a man almost drowned on a ride in April
The Thunder River Rapids ride was built in 1986 and is said to be a 'moderate' with a maximum speed of 45km and hour
Children over two years old are allowed to go on the ride with an adult
Shocked US Olympic gold medalist Matthew Centrowitz said he had been on the ride just a few minutes before the accident (pictured)
RECENT SAFETY INCIDENTS AT DREAMWORLD
June 2009: Helicopter crashes into Dreamworld carpark, injuring the pilot and four Taiwanese passengers
2011: Two separate reports of Bengal tiger Kato biting handlers at the Tiger Island attraction - once in May and once in September
November 2013: More than 7000 people evacuated from Dreamworld in under an hour after a bushfire came close to the facility
April 2016: A passenger on the Rocky Hollow Log Ride nearly drowned after being thrown from the attraction and suffering lacerations to his head
'Dude, just got off a ride 15 mins ago that has 1 person seriously injured and 2 others trapped,' he wrote on Twitter.
The Thunder River Rapids ride was built in 1986 and is said to be a 'moderate' with a maximum speed of 45km/h, according to Dreamland.
Children over two years old are allowed to go on the ride with an adult.
People sit on circular rafts that seat six.
Riders on the Thunder River Rapids ride sit on circular rafts that can seat six people
The Thunder River Rapids ride (stock picture) is described as a moderate family ride by Dreamworld