MANILA, Philippines — A Qantas jumbo jet carrying 345 passengers made an emergency landing today with a gaping hole in its fuselage after a mysterious “explosive decompression,” officials said.

There were no injuries, but some passengers vomited after disembarking the Boeing 747-400, the Manila International Airport Authority deputy manager for operations, Octavio Lina, said.

The cabin’s floor gave way, he said, exposing some of the cargo beneath and part of the ceiling collapsed.

“There is a big hole on the right side near the wing,” he said, adding it was 2.5 to 3 yards in diameter.

A report by the Manila International Airport Authority, quoting pilot John Francis Bartels, said the plane suffered an “explosive decompression.” Australia’s air-safety investigator said an initial investigation suggested “a section of the fuselage separated.”

The chief executive officer of Qantas, Geoff Dixon, Australia’s largest airline, praised the pilots and the rest of the 19-person crew for how they handled the incident.

“This was a highly unusual situation and our crew responded with the professionalism that Qantas is known for,” he said.

Flight QF30, from London to Melbourne, had just made a stopover at Hong Kong.

Passengers who talked to the media at the airport described hearing an explosion, and then oxygen masks were released.

“One hour into the flight there was a big bang, then the plane started going down,” a passenger, Marina Scaffidi, 39, from Melbourne, told The Associated Press by phone from Manila airport. “There was wind swirling around the plane and some condensation.”

She said the hole extended from the cargo hold into the passenger cabin.

“The plane kept going down not too fast, but it was descending,” Ms. Scaffidi said, adding the jetliner was over the South China Sea when the staff informed passengers they were diverting to Manila.

“No one was very hysterical,” she said.

An architect from Melbourne, Michael Rahill, 57, said the bang sounded “like a tire exploding, but more violently.”

June Kane of Melbourne described how parts of the plane’s interior broke apart in the depressurized cabin.

“There was a terrific boom and bits of wood and debris just flew forward into first (class) and the oxygen masks dropped down,” she told Australia’s ABC Radio. “It was absolutely terrifying, but I have to say everyone was very calm.”

The passengers were taken to several hotels while waiting for another plane to Melbourne late today, Wantas said. The plane was towed to a hangar at Manila.

Qantas — Australia’s largest domestic and international airline — boasts a strong safety record and has never lost a jet to an accident, although there were crashes of smaller planes, the last in 1951.

“Qantas’ reputation in the field of aviation safety is recognized worldwide,” the airline says on its Web site.

However, the airline has had a few scares in recent years. In February 2008, a Qantas 717 with 84 passengers on board sustained substantial damage in a heavy landing at Darwin, Australia.

In addition, union engineers — who have held several strikes this year to demand pay raises — say that safety is being compromised by low wages and overtime work.

The head of the police Aviation Security Group, Chief Superintendent Atilano Morada, said his officers, including explosives experts, may assist in the airline’s investigation.

“So far, they don’t want us to touch it, so we will respect the aircraft owner. But we will make our personnel available if they need assistance in the investigation,” he said.

Qantas touts itself as the world’s second-oldest airline, founded in 1920. As of December 2007, Qantas was operating 216 aircraft flying to 140 destinations in 37 countries, though in recent months it has announced it will retire some aircraft and cancel some routes — as well as cutting 1,500 jobs worldwide — due to skyrocketing fuel prices.

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Associated Press writers Oliver Teves and Teresa Cerojano contributed to this report.