BRISBANE, Australia >> A helicopter carrying American tourists crashed at a coral-viewing site on Australia’s Great Barrier Reef, killing two passengers from Hawaii and injuring two others from Colorado, police said.

The helicopter pilot pulled one passenger from the wreckage after Wednesday’s crash but desperate attempts to revive the 65-year-old woman failed, Police Inspector Ian Haughton said Thursday. A 79-year-old man also died despite bystanders’ attempts to resuscitate him, Haughton said.

A 34-year-old man and a 33-year-old woman were taken to the Australian mainland for treatment of non-life-threatening injuries, he said. All four tourists knew each other.

The five-seat, single-engine Eurocopter EC120 Colibri crashed 65 kilometers (40 miles) northeast of the Whitsunday Islands near a pontoon that has underwater viewing chambers to see coral and is a popular tourist destination.

The U.S. Embassy in Australia said in a statement it was aware that two U.S. citizens had died and was “providing all appropriate consular assistance.”

Whitsunday Air Services said the helicopter was approaching the pontoon to land when it crashed.

The company had suspended operations as it works with authorities to determine the cause of the crash.

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

The Australian Transport Safety Bureau confirmed a crash investigation was underway.