A man has died after a helicopter crashed into the roof of a Cairns hotel, sparking a massive fireball and the evacuation of up to 400 people.

Emergency services were called to the Double Tree Hotel by Hilton about 1:50 a.m. (local time) following reports a twin engine helicopter crashed into a roof.

The pilot and only occupant of the helicopter was declared dead at the scene, with forensic investigators working to formally identify him, police said.

The company that owns the helicopter reportedly said the flight was “unauthorized.”

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

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

The Courier-Mail earlier reported no flight plan had been created.

It remains unclear whether the pilot was an employee.

NewsWire has contacted Nautilus Aviation for further comment.

A bystander, Veronica Knight, said the helicopter was going incredibly fast before it crashed into the hotel.

“It seemed to come from the pier over there and straight down over the sea, straight, and it was going really, really fast. I thought, ‘wow, that doesn’t look right’,” she told Sunrise on Monday morning.

“It was pretty low, so I got … I was trying to video it, but it went too fast. And then it disappeared for about five to 10 minutes. Then I got a shock, it came back again.

“It was coming back along the sea again. And The Esplanade, and then all of a sudden it suddenly veered to the right.

“I just saw a big explosion and, like, huge fire and I thought, yeah, it’s just hit straight into the motel.”

A fire broke out on the roof of the hotel following the crash and up to 400 people were evacuated; however, no one on the ground suffered any injuries.

Paramedics earlier confirmed they were called to the scene just after 2 a.m. and assessed a male patient with life threatening injuries.

Another male in his 80s and a woman in her 70s were treated and taken to Cairns Hospital in a stable condition.

Seven reports the pair were staying in the room below the crash and were treated for shock.

Queensland Ambulance Service Far Northern Region senior operations supervisor Caitlin Dennings said witnesses had told her the incident “sounded like a bomb.”

“The helicopter impacted the roof of the hotel however two propellers have dislodged from the helicopter landing on the Cairns Esplanade, and there was a second propeller located in the hotel pool on the bottom floor,” she told The Cairns Post.

Police have advised the public to avoid the area.

An exclusion zone remains in place and includes The Esplanade and Minnie, Abbott and Florence streets.