The plane was forced to make an unscheduled landing at Exmouth
A passenger plane has made an emergency landing in Western Australia after some 40 people were hurt following a "sudden change in altitude", officials say.
The Qantas Airbus A330-300 flying from Singapore to Perth with 313 people on board landed at Learmonth Airport near Exmouth after making a mayday call.
Qantas said there was no sign yet as to what caused the altitude change, but officials suspect it was turbulence.
Emergency services, including medical personnel, met the plane on landing.
Three cabin crew and more than 30 passengers sustained injuries, 15 of them serious, including fractures and lacerations, officials said.
Several people were taken to the hospital in Exmouth.
The Royal Flying Doctor Service also sent two aircraft to Exmouth to help transport the injured to the state capital Perth, about 1,100km (700 miles) south of the town, if necessary.
The Australian Air Transport Safety Bureau said the plane had been cruising in level flight when it experienced a "sudden in-flight upset" which resulted in injuries to a number of cabin crew and passengers, primarily in the rear of the aircraft.
They put two people in the seats in front of us - when I looked up they had their backs on the ceiling
Nigel Court, passenger
The pilot declared a mayday and diverted the plane to make an emergency landing at the remote Learmonth airport on the north-western Australian coast, "where it landed without further incident", the statement added.
One of the passengers, Nigel Court, said the sudden change in altitude had caused mayhem on board.
"They put two people in the seats in front of us. When I looked up they had their backs on the ceiling. My wife was the same - she crashed head first into the roof above us," he told the Reuters news agency.
"We had either the captain, or the first officer, in the area just behind us and he got caught unaware as well as, as well as a number of the cabin crew, one of who broke his leg as well."
Qantas said there were no details available at this stage as to what caused the altitude change, but one local police officer said it was severe turbulence.
"We have had some information that it possibly was turbulence, but we haven't had that confirmed at this stage," Sgt Clifford told ABC.
However, Western Australia Police Commissioner Karl O'Callaghan later told the Sydney Morning Herald that he understood the incident had been caused by "some sort of systems failure".
He said his force's State Crisis Centre in Perth had been activated. Seven ATSB investigators are also preparing to travel to Learmonth in order to investigate the incident.
Qantas is sending two smaller planes to the airport to bring stranded passengers to Perth.
The Australian flag-carrier prides itself on having a good safety record, but a spate of recent incidents has dented its image, correspondents say.
7 October: Airbus A330 makes emergency landing in Western Australia after "sudden change in altitude" injures up to 40 people
2 Aug: 767 returns to Sydney after hydraulic fluid leak in wing
28 July: 737 returns to Adelaide with landing gear cover problem
25 July: 747 diverted to Manila after hole appears in fuselage
In July, a Qantas Boeing 747 flying from Hong Kong to Melbourne was forced to make an emergency landing after an oxygen cylinder caused an explosion which blew a large hole in the fuselage.
Later that month, one of the airline's Boeing 737s returned to Adelaide after a landing gear bay door failed to close. Days later, a Boeing 767 bound for Manila needed to return to Sydney after a hydraulic fluid leak was detected.
The Australian Civil Aviation Safety Authority subsequently launched a review of the airline. Officials said they had no evidence of falling safety standards, but that it was "prudent" to take a closer look.
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