Investigators are working to determine how a helicopter crashed into waters off Queensland’s Whitsunday Islands on Wednesday, killing two international tourists.

The Civil Aviation Safety Authority says five people were aboard the Whitsunday Air Services-owned Eurocopter 120 when it went down near Hardy Reef Pontoon on Wednesday afternoon.

Queensland Police confirmed two people had died in the crash at about 3.35pm local time on Wednesday, while three people were being treated for non-life-threatening injuries.

“A man and a woman who are believed to be international tourists were recovered from the helicopter and pronounced deceased at the scene,” a Queensland police statement said on Wednesday night.

Three other people, including the male pilot and a male and female passenger, also believed to be from overseas, would be taken by sea to a medical facility for treatment.

The helicopter pontoon at Hardy Reef, where a chopper crashed on Wednesday afternoon. Photo: cqplanespotting.blogspot.com.au (file)

It is understood the helicopter crashed into water 250 metres from the pontoon.

Local media reported that onlookers plucked survivors from the sinking helicopter and performed CPR on two of the passengers while listening to instructions from paramedics via phone.

Despite their efforts, the critically injured man and woman could not be saved, The Courier Mail reported.

The Australian Transport Safety Bureau (ATSB) issued a release on Wednesday evening confirming a crash investigation was being launched.

“A team of Transport Safety Investigators will soon travel to the accident location to commence the evidence collection phase of the investigation,” an ATSB statement said.

“There, investigators will interview witnesses, examine any available recorded data, review operational records and technical documentation amongst other activities.”

Police will assist the ATSB with the investigation and recovery of the aircraft.

Whitsunday Air Services said that the helicopter was on a final approach to land at its Hardy Reef Heliport when it crashed.

“We are extremely saddened by this incident and our deepest condolences are with the families of all of the passengers,” it said in a statement.

“Whitsunday Air Services is continuing to work with the Queensland Police, the ATSB and CASA to assist with their investigations. Whitsunday Air Services will be suspending all operations while a full review process is undertaken.”

The pontoon, 65km north-east of the Whitsundays, allows underwater viewing chambers, with tourist operators in the area saying Hardy Reef offers an excellent combination of reef, coral and fish life for tourists.

The well-known Heart Reef is also nearby.

The deadly Eurocopter 120 crash came a day after the final investigation report into the partial engine power loss and ditching of a Robinson R44 helicopter near Hamilton Island on November 8 last year.

In that incident, the pilot landed the helicopter on the water, with the emergency floats deployed, shut down the engine, and applied the rotor brake.

The emergency locator transmitter was activated and passengers were instructed to prepare to inflate their life jackets and prepare to evacuate the helicopter.

All onboard were rescued about an hour later, while the helicopter later sank and was unable to be recovered.

-with AAP