INQUIRER Global Nation

MANILA, Philippines--An oxygen cylinder is missing from a Qantas 747 after a mid-air explosion punched a hole in its fuselage, an Australian investigator said Sunday.

"It is too early to say whether this was the cause of the explosion," Neville Blyth from the Australian Transport Safety Bureau told a media briefing.

"But one of the cylinders which provides back up oxygen is missing," he said.

"I can't speculate as to include the probability of that cylinder having caused the damage. All I am reporting is the factual information that in the vicinity of the damage, we are missing one cylinder," he said.

The Qantas Boeing 747 was flying from Hong Kong to Melbourne on Friday when an explosive bang led to a sudden loss of air pressure in the cabin.

The plane plunged 6,000 meters (20,000 feet) before stabilizing and then making an emergency landing in the Philippines capital Manila, where stunned passengers saw a three-meter (10 foot) rip in the fuselage next to the right wing.

Blyth said the investigation would take two to three days and a full report on the findings "should be released in two to three months."

He said investigators had ruled out terrorism saying: "There is no evidence of a security related event here.

"Philippine bomb sniffing dogs have inspected the baggage and found no materials of concern," he added.

Blyth would not be drawn on the oxygen cylinder which is roughly the size of a diver's scuba tank and he would not say how many were on the aircraft.