Concerns about safety and maintenance at Dreamworld were raised 18 months ago, the Australian Workers' Union says.
Concerns about safety at Dreamworld have been raised since last April, the Australian Workers' Union says.
The union, which claimed it represents a "substantial" number of workers employed at Dreamworld, has been repeatedly making representations to Dreamworld "about issues our members have regarding the operation and maintenance of various equipment, including rides," AWU Queensland Secretary Ben Swan told SBS News.
"They have not been cooperative as far as we are concerned with respect to the issues the union has been raising on behalf of its membership," he said.
The AWU made a Right to Information claim to Dreamworld owner Ardent but it was refused, Mr Swan said.
"The absence of collaboration and cooperation leads me to the view that there has not been much productivity between us and the employer about what are now seen to be very serious issues," he said.
Mother told Dreamworld 'someone will get seriously injured or killed'
Dreamworld has deleted all of its reviews on its Facebook page.
A review from earlier this month, now circulating on social media, from a woman named Tracey Christensen claimed several rides had safety issues.
"Went to the wipeout [and was told] sorry operational issues, the kids get off [ride] the claw and said one of their belt buckles come undone right up in the air," Ms Christensen claimed.
She also said there were issues with the Tower of Terror, Wipeout and log ride.
"All I want now is my money back because having 5 rides with operational issues is not good enough," she said in the October 10 review.
"Someone will get seriously injured or killed one day!"
Amusement rides are 'very safe': engineer
The chance of getting killed on an amusement park ride is one in 834 million, an engineer says.
The rides are safer than flying on a plane or going scuba diving, according to David Eager, who sits on Standards Australia's amusement rides and devices committee.
"The number of deaths on an amusement ride is one in 834 million rides. Aeroplanes is one in 125 million rides. You go scuba diving and that's one in 200,000 dives," he told ABC radio on Wednesday.
"Statistically, they are very safe."
But Mr Eager said people do get thrown out of rides and the deaths on Tuesday were a tragedy.
"When we get catastrophic events like this, where people are killed, they (the risks) are now amplified in people's minds," he said.
Four people died when a raft flipped on the Thunder River Rapids ride at the Dreamworld theme park on the Gold Coast.
- with AAP