Australian police are investigating the cause of a "traumatic" helicopter crash in North Queensland that claimed the lives of two American tourists and injured three other individuals.

The tourists, a 65-year-old woman and a 79-year-old man, were visiting from Hawaii on Wednesday afternoon when the Airbus H120 crashed into a remote coral-viewing pontoon, killing them and injuring the others on board, Queensland police said.

The remaining passengers, a 34-year-old man and a 33-year-old woman from Colorado, and the pilot were taken to the Australian mainland to be treated for non-life-threatening injuries, police said.

"The four passengers are from the U.S.A. and are known to each other," Queensland State Police Inspector Ian Haughton said Thursday. "An independent, transparent and robust investigation is currently underway." That inquiry will involve the Australian Transport Safety Bureau.

"This is a traumatic experience for anyone involved," he added.

Haughton could not provide any additional details about the crash or the surviving passengers, but he said the pilot, 35, had pulled one of the dead from the wreckage, while a witness on the scene performed CPR on others.

The helicopter operator, Whitsunday Air Services, said it is "devastated by this accident and our thoughts and condolences are with the passengers and their families."

"At this early stage, we are unaware of the how the accident occurred, however we are providing the authorities with all of the relevant information to assist with answering their inquiries," the company said in a statement. "We are working to assist those affected by the accident where possible through the extensive support networks of Hamilton Island where the passengers were staying."

The company said it would suspend air-service operations "until a full review of the accident is undertaken."

ABC News' Kirit Radia contributed to this report.