An air safety investigation into the emergency landing of a Qantas plane in the Philippines last month has blamed an exploding pressurised oxygen cylinder.

The interim report released by the Australian Transport Safety Bureau on Friday says the sudden release of pressure from the cylinder blew a 1.5m hole in the plane's fuselage, forcing a safe but emergency landing in the Philippine capital, Manila, on July 5.

Julian Walsh, acting executive director of the bureau, did not explain why the cylinder – one of seven on board - exploded.

Qantas Airways said its "own investigations agree with the ATSB's preliminary conclusions".

The Boeing 747-438 aircraft, carrying 365 people from London to Melbourne, lost cabin pressure and rapidly descended thousands of metres over the South China sea.

No one was injured in the incident, 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.