Philippines ? Australian investigators were exploring the possibility that an oxygen cylinder could have exploded midflight on the Qantas jumbo jet that made a harrowing emergency landing in the Philippines with a giant hole in its fuselage, an official said today.

The Boeing 747-400 had 346 passengers aboard when it was shaken by what passengers described as an explosion. Oxygen masks dropped from the ceiling as the plane descended rapidly and debris flew through the cabin from a 9-foot hole that suddenly appeared.

The plane, en route from London to Melbourne, Australia, had made a stopover in Hong Kong and was cruising at 29,000 feet before the trouble forced it to land at Manila’s Ninoy Aquino International Airport on Friday. There were no injuries among the passengers and crew.