The pilot who died when this helicopter crashed into a Cairns hotel in a fiery late-night incident was on an “unauthorised” flight, police say.

The man – who is yet to be identified – was the sole occupant of the twin-engine chopper that crashed into the DoubleTree by Hilton about 1.50am on Monday, setting off an enormous fire.

“It was like a fuel tank exploding,” tourist Veronica Knight said, describing how the helicopter flew around “really fast” before hitting the hotel in a “massive explosion”.

Up to 400 people were evacuated from the hotel when the helicopter crashed into its roof.

Among them were a man in his 80s and a woman in her 70s – who had been asleep in the room below where the aircraft hit. They were taken to hospital to be treated for smoke inhalation, and were the only people on the ground who needed medical treatment.

Queensland Police said they believed the incident was isolated, and there was no threat to the community. But they are not yet sure if it was deliberate or an accident.

“Forensic investigations are under way to formally identify them,” police said of the pilot.

Australian Transport Safety Bureau chief commissioner Angus Mitchell said it was a traumatic incident.

“We have certainly had a look at the room that was impacted when we had two people asleep at the time. No doubt that has been a very traumatic experience for them, and also for the family and friends of the person who was deceased,” he said.

“Once we do have an identity of the person involved, then we will start looking a little bit more closely on all the things that may have contributed to what unfolded last night.”

The helicopter took off from nearby Cairns Airport only minutes before it crashed into the hotel on Cairns’ Esplanade. Rain at the time is believed to have affected visibility.

An exclusion zone was declared on the Esplanade in Cairns. Photo: Queensland Police

Charter company Nautilus Aviation confirmed 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 on Monday.

“As we continue to fully support the ongoing investigation, we will not be making further comments at this time.”

In the immediate aftermath of the late-night crash, police set up an exclusion zone set up encompassing The Esplanade and Minnie, Abbott and Florence streets. It remained active until well into Monday.

Knight, who was visiting from Sydney, said hotel guests “had no idea what happened”.

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

She said she’d 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.”

Earlier, Queensland Ambulance senior operations superviser in Cairns, Caitlin Denning, said 300 to 400 people were evacuated from the DoubleTree hotel as crews arrived on the scene.

“At the time, it was too unsafe for us to enter the hotel to view the [crash site],” she said.

“The helicopter impacted the roof of the hotel. However, two propellers have dislodged. One landed on the Cairns Esplanade and there was a second propeller located in the hotel pool on the bottom floor, and it was on fire.”

Denning said the noise of the impact was frightening.

“There were reports of it sounding like a bomb – and, seeing the fire and smoke, a lot of the occupants of the hotel were unsure of the situation,” she said.

“There is a lot of unease here.”

Queensland Police’s forensic crash unit and the ATSB will prepare a report for the coroner.

-with AAP