Details are emerging about the mystery identity of the pilot who stole a helicopter and crashed into a waterfront hotel roof in Cairns.

The pilot was killed when the chopper slammed onto DoubleTree by Hilton and caused a “massive explosion” very early on Monday, forcing the evacuation of hundreds of guests.

A delicate operation to remove the destroyed wreckage from the building was completed on Tuesday morning (AEDT).

The Australian reports the man who took the aircraft from Cairns Airport was believed to be an employee of Nautilus Aviation.

The R44 Robinson helicopter belonged to Nautilus and was taken from a general aviation hangar at the airport about 1.48am.

It was reportedly flown low and erratically for about four minutes before crashing in the no-fly zone of Cairns Esplanade, writes The Australian.

Charter company Nautilus Aviation confirmed on Monday the use of the helicopter was “unauthorised”.

“Nautilus Aviation are working closely with Queensland Police, the Australian Transport Safety Bureau and other authorities as they investigate the unauthorised use of one of our helicopters in the early hours of this morning,” it said.

Nautilus Aviation chief executive Aaron Finn told The Australian all pilots who worked for Nautilus were safe and accounted for.

But he could not rule out the possibility someone else in the company was responsible.

“We have quite a lot of staff in the organisation. We can’t identify (the person responsible) from CCTV footage, it’s very dark,” he said.

There are still big questions to answer such as how the man was able to access the helicopter from the secure hangar and where he was flying.

Fire on the roof of the waterfront hotel. Photo: AAP

‘Massive explosion’

An emergency exclusion zone was set up in the heart of the tourist hub after propellers were dislodged in the 2am crash, with one landing on the main street and another in the hotel pool.

The identity of the pilot — the helicopter’s sole occupant — is yet to be formally confirmed along with the circumstances surrounding the “unauthorised” flight.

Asked if the crash was deliberate, Queensland Police’s Acting Chief Superintendent Shane Holmes said: “Unknown at this stage, but we’ll investigate all lines of inquiry.

“There is no further threat to the community and we believe this was an isolated incident.”

Authorities did not think the helicopter was in the air for long but were unable to comment on how fast it had been travelling, its flight plan or whether the pilot had a licence.

The Nautilus Aviation hangar at Cairns Airport. Photo: AAP

A witness, Veronica Knight described how the twin-engine chopper flew around at speed before hitting the hotel in a “massive explosion”.

“It was like a fuel tank exploding,” she said.

“We saw the rotor on the ground. I wasn’t far away. It could have got me.”

The Australian Transport Safety Bureau sent crash investigators to the scene on Monday.

“Once we do have an identity of the person involved then we’ll start to looking a little bit more closely on all the things that may have contributed to what unfolded … but it’s only very early days,” the bureau’s chief commissioner Angus Mitchell said.

Knight said she saw the helicopter fly around for about 15 minutes, twice going past her “really fast”.

The Sydney tourist said she had never seen a helicopter travel so quickly.

“It came back real fast then went into the hotel. I was very scared,” she said.

“It was like an army helicopter but faster. Like a warplane, like it was going to come in and bomb you.”

Up to 400 people were evacuated from the hotel and taken to another venue in Cairns’ city centre after the crash.

Two hotel guests, a man in his 80s and a woman in her 70s, were taken to Cairns Hospital in a stable condition for smoke inhalation.

“I do believe they were asleep at the time and there were some windows that may have been impacted as a result of the incident occurring,” Acting Supt Holmes said.

“I think it’s by pure luck that no one else was injured. It could have been worse.”

Police declared a Public Safety Preservation Act, an exclusion zone.

A fire prevented emergency crews entering the hotel immediately.

DoubleTree by Hilton management said all guests and staff were safely evacuated from the premises.

“We are actively arranging alternate accommodations for these guests for this evening,” a statement said.

Queensland Premier Steven Miles described it as a “terrifying event”.

“I can’t imagine how scary it would be to be asleep and to hear that bang and to have to be evacuated.”

-with AAP