Four people are dead and another three are in a critical condition after two helicopters collided on Australia's Gold Coast near Sea World on Monday.
Emergency services were called to the scene at about 2pm after the two helicopters crashed mid-air.
A witness told 7NEWS the accident happened while one was taking off and the other was landing.
"As a result of that four people have lost their lives today and we have three others critical in hospital," Police Inspector Gary Worrell said.
A Queensland Ambulance spokesman said 13 patients were being assessed.
According to 7NEWS, one helicopter successfully landed on a sandbank while the other ended up upside down in the water. Images from the crash site show two helicopters with serious damage. The words 'Sea World Helicopters' were clearly visible on one of the aircraft.
One witness told ABC News she thought it was a car crash at first.
"Then we heard the helicopter propellers slowly getting lower, and then we heard another massive big bang," she said.
"My daughter saw them. People on both. Landed on the sand not in Sea World thank goodness. Just praying for all," another witness said.
The Australian Transport Safety Bureau (ATSB) said an investigation is now underway.
"Transport safety investigators with experience in helicopter operations, maintenance and survivability engineering are deploying from the ATSB's Brisbane and Canberra offices and are expected to begin arriving at the accident site from Monday afternoon," a statement read.
"During the evidence-gathering phase of the investigation, ATSB investigators will examine the wreckage and map the accident site. Investigators will also recover any relevant components for further examination at the ATSB's technical facilities in Canberra, gather any available recorded data for analysis, and interview witnesses and other involved parties," it said.
"The ATSB asks anyone who may have seen the collision, or who witnessed the helicopters in any phase of their flights, or who may have footage of any kind, to make contact via witness@atsb.gov.au at their earliest opportunity. "
