Two men and two women have been killed on a ride at a theme park.1rodeTwo victims were thrown from a raft on the Thunder River Rapids ride at Dreamworld on Queensland’s Gold Coast, while two others were trapped inside, officials said. The Australian park in Coomera has been closed and an investigation is under way.

Dreamworld bills itself as Australia’s biggest theme park with more than 50 rides and attractions. The Thunder River Rapids ride whisks visitors in circular rafts along a fast-moving artificial river. Dreamworld describes it as a “moderate thrill” attraction.

Queensland Ambulance spokesman Gavin Fuller blamed a “malfunction” for the accident.

The victims have not been named but are reported to be two women aged 32 and 42 and two men aged 38 and 35. Australia’s 9News reported that they were possibly from the same family.