Investigators looking at whether an exploding oxygen bottle blew a large hole in the side of a Qantas 747 said part of a bottle burst into the plane's cabin and partly moved a door lock. The Qantas 747-400 suffered a loss of cabin pressure during a flight from Hong Kong to Melbourne last Friday, forcing the plane to make an emergency descent from 29,000 feet to 10,000 feet before landing safely in Manila in the Philippines.

Australian Transport Safety Bureau (ATSB) investigators have been examining oxygen bottles in the plane's hold, and said part of one bottle had blown through the floor of the passenger compartment and moved a door handle towards the open position.

"There was never any danger of the door opening," ATSB director Julian Walsh told reporters.

He said the impact sheared the door handle, which was designed to break if someone attempted to open the doors in flight, and the door latches remained locked.

Qantas has been ordered to check all oxygen cylinders on its fleet of 747s.

The plane has been moved into a hangar in Manila as investigators continue to examine data from the plane's flight data recorder, which shows flight QF30 made an emergency descent from 29,000 feet to 10,000 feet in five minutes.

Passengers reported a loud bang before the depressurisation, and some complained of faulty oxygen masks during the emergency descent.

Walsh said investigators had examined the oxygen masks and found a small number of masks did not deploy properly.

"The investigation team is still examining the oxygen system," he said, to see if the oxygen supply was enough to last the five minutes of the emergency descent to 10,000 feet.

All 346 passengers and 19 crew disembarked safely in Manila.