An investigator says a valve and other fragments that could be from a missing oxygen tank have been found in a Qantas jet that had its fuselage ripped open mid-flight.

The missing tank has become the focus of the probe into what tore open a car-sized hole in the plane 29,000 feet and forced an emergency landing in the Philippines on Friday.

Neville Blyth, a senior investigator from the Australian Transport and Safety Bureau, told a news conference Monday that the fragments would be tested to see if they came from the tank, which is designed to provide passengers emergency oxygen.

He says the fragments were found close to where the missing tank was stored.

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