Sydney- A computer malfunction was Tuesday blamed for a Qantas passenger jet en route from Singapore to Perth plunging in altitude and injured 46 passengers a week ago.

The Airbus A330 serving the October 7 flight suddenly lost altitude and made an emergency landing at Learmonth military base, 1,260 kilometres north of Perth.

The Australian Transport Safety Bureau (ATSB) said the plane's "air data inertial system" was the cause of the problem and that Airbus operators around the world had been alerted to the problem.

The ATSB said the air data computer sent erroneous information to the flight control computer, causing the autopilot to disconnect.

A dozen people were kept in hospital overnight after the incident but all have now been released. (dpa)