Sydney, Mar 22 (IANS): Australian aviation authorities on Thursday launched a full investigation after a helicopter crashed in the Great Barrier Reef killing two American tourists.

The single-engine airbus H120 (formerly known as a Eurocopter 120b) was reported to have crashed into the waters on Wednesday 250 metres away from a remote pontoon, used mostly by snorkelers and scuba divers, at Hardy Reef 65 km north of the Whitsunday Islands, Xinhua news agency reported.

Three others, including two passengers and a pilot of the plane, were injured in the crash.

Those who saw the crash "heroically" recovered the three from the water and performed cardiopulmonary resuscitation (CPR) on them while waiting for emergency paramedics to arrive on the scene, Queensland police said on Thursday.

Whitsunday Air Services, the company which owned the crashed helicopter, said they were extremely saddened by the incident.

"Whitsunday Air Services is continuing to work with the Queensland Police, the Australian Transport Safety Bureau and the Civil Aviation Safety Authority to assist with their investigations."

One of the three survivors remain in serious condition, while the other two have only minor injuries.

The latest incident came just four months after another Whitsunday Air Services helicopter sank near Hamilton Island after the engine lost power and was forced to make an emergency landing.

Although the pilot and passengers were rescued, the Robinson R44 helicopter was not recovered.