An oxygen cylinder caused the explosion that blew a car-sized hole in a Qantas jet last month, forcing an emergency landing, air safety officials said Friday.

The release of the interim report by Julian Walsh, acting executive director of the Australian Transport Safety Bureau, confirmed earlier suspicions by investigators that an exploding oxygen tank was the cause.

The Boeing 747-438 aircraft, carrying 365 people, was flying over the South China Sea July 5 when the explosion blew a hole in the fuselage five-feet in diameter, causing a loss of cabin pressure.

Walsh said one of the seven emergency oxygen cylinders below the cabin floor had exploded, but did not say what caused the tank to burst.

"On the basis of the physical damage to the aircraft's forward cargo hold and cabin, it is evident that the number 4 passenger oxygen cylinder sustained a failure that allowed a sudden and complete release of the pressurized contents," Walsh told reporters in releasing the report.

The plane — en route from London to Melbourne, Australia — rapidly descended thousands of feet and flew about 300 miles to Manila, where it made a successful emergency landing.

No one was injured, but questions were raised about the much-lauded safety of Qantas Airways, which has never lost a jet aircraft because of an accident.

In the weeks after the incident, Qantas planes experienced a number of other problems, including a loss of hydraulic fuel that led to an emergency landing, failure of landing gear, and detached panels.

The problems prompted the Civil Aviation Safety Authority, Australia's aviation agency, to launch a review of Qantas Airways' safety standards.

Qantas earlier this month temporarily pulled six planes from service because of irregularities in maintenance records. Qantas said it was a record-keeping issue and there were no safety implications for the aircraft.