Four people have died after a mid-air collision between two helicopters near Seaworld on Australia's Gold Coast.

The nine other passengers aboard the two aircraft were all treated for injuries, Queensland's ambulance service said.

Three passengers—a woman and two young boys—have been taken to the hospital in critical condition.

The Australian Transport Safety Bureau (ATSB) has said it will investigate.

The collision took place around 14:00 local time (04:00 GMT) along a tourist strip known as Main Beach, about 75 kilometers (47 miles) south of Brisbane.

Gary Worrell of Queensland police told reporters that one helicopter appeared to be taking off as the other one was landing.

He said the four deaths and three serious injuries had all occurred in the same aircraft.

"It's a difficult scene," he said. "Due to the area it's located in, on the sand bank, it was difficult to gain access and get our emergency services to the scene to manage it appropriately."

Images from the crash site show debris strewn around the area and a mangled helicopter apparently lying upside down opposite the SeaWorld resort.

The other helicopter has the popular marine park's logo emblazoned on its side and appears to have safely landed after the collision.

Seaworld Drive, the main access road to the marine park, has been closed off to traffic by local police.

They urged motorists and pedestrians to avoid the area as first responders inspect the scene.

Investigators from the ATSB's offices in Brisbane and Canberra are being deployed to the scene to gather evidence, examine the wreckage, and interview witnesses.

ATSB Chief Commissioner Angus Mitchell has also asked eyewitnesses who saw the collision or the helicopters in flight to contact investigators.

A preliminary report will be made public in the next six to eight weeks, with a final report to follow once the investigation is complete, he added.

The Gold Coast region is currently in its peak tourist season, with children on their summer breaks.