Police say two American tourists were killed and two other Americans sustained minor injuries when a helicopter crashed on Australia's Great Barrier Reef.

Police Inspector Ian Haughton said on Thursday the pilot pulled one of his four passengers from the wreckage after the crash on Wednesday at a coral-viewing pontoon northeast of the Whitsunday Islands. But desperate attempts to revive the 65-year-old woman failed.

Haughton says a 79-year-old man also died despite bystanders' attempts to resuscitate him.

A 34-year-old man and a 33-year-old woman were taken to the Australian mainland for medical treatment of injuries that did not threaten their lives, he said. All four tourists knew each other.

Whitsunday Air Services suspended operations as it works with authorities to determine the cause of the crash.