According to Australian media reports, an 18-year old, in her first day on the job, was operating the emergency stop button on the Dreamworld ride that killed four people.
It's also understood the water levels on the ride were lower than normal and a sensor should have triggered an emergency stop, but didn't.
Two men and two women were killed on the Thunder River Rapids ride on Tuesday when their raft crashed and flipped over. Two children were also in the raft, but survived.
A candlelit vigil was held outside the theme park on Wednesday night to honour the victims of the accident.
Australia correspondents Jason Morrison and Sophie Lowery joined Paul Henry to talk about the incident.
Watch the video.
