Sydney, Oct 8 (DPA) It would take a month to find out why a Qantas flight dropped altitude dramatically, injuring at least 36 passengers before it made an emergency landing, investigators said Wednesday.The Airbus A330 from Singapore to Perth, with 303 passengers and 10 crew, put out a mayday call Tuesday before making an emergency landing at Learmonth military base, 1,260 km north of Perth.

At least 36 passengers were injured “following a sudden change in altitude” over the west Australia coast.

Qantas would not speculate on the cause of the plunge - according to one passenger the plane dipped 8,000 feet (2,440 metres) in about 10 seconds - but West Australian Police Commissioner Karl O’Callaghan spoke of “some sort of system failure”.

Ian Sangston from the Australian Transport Safety Bureau told national broadcaster ABC that even an initial finding in the investigation into what happened aboard Flight QF72 would take a month.

“We look at the aircraft maintenance and history and certainly we look at other operators of the A330 in this case and other countries’ records because we want to know if there is a history of any particular thing like this,” he said.

Mark Bell said the frightening plunge came without any warning.

“The poor kid next to us, we watched him hit the ceiling and sit there for about three seconds until his dad dragged him back into his seat,” he told the ABC on his arrival at Perth airport.

None of the 36 passengers in hospital has life-threatening injuries, but they did suffer cuts, bruises and broken limbs.