(CNN) - The Australian air safety agency is investigating Saturday the emergency landing of a Qantas Boeing 747 in the Philippines after a hole in the fuselage made the plane lose cabin pressure.
Officials from two U.S. transportation agencies said initial findings indicate no act of terrorism was involved.
According to early reports, a section of the fuselage separated in the forward cargo compartment, the Australian Transport Safety Bureau (ATSB) said in a written statement.
"Our preliminary checks on this indicate that there was no corrosion anywhere near where this hole occurred in the aircraft," Geoff Dixon, Qantas CEO, said in Sydney.
Video of the plane after it landed on Friday showed a large hole where the leading edge of the wing attaches to the fuselage.
The section of the fuselage separated at about 29,000 feet, and the cabin began to rapidly decompress, ATSB said in the statement released Friday.
The crew brought the plane down to 10,000 feet and diverted the aircraft to Manila International Airport, where it landed safely about 11:15 a.m. (11:15 p.m. ET Thursday).
The airline said it received no reports of any injuries among the 346 passengers and 19 crew members.
Dixon called the incident a "hugely serious issue" and one that investigators would sort out. "We can't speculate on what happened."
Oxygen masks were deployed during the emergency. Passengers said their ears popped because of the plane's rapid descent to a lower altitude.
"There was an almighty crack," one passenger said. "We dropped a bit in the air, but other than that it was fine."
"There was a big bang," said another. "I knew there was a hole somewhere, but I didn't know what was going on."
The Boeing 747-400 flight originated in London. It had just taken off from Hong Kong and was en route to Melbourne, Australia, when it was forced to land.
A U.S. Transportation Security Administration official, who asked not to be identified because his agency is not leading the probe into the incident, told CNN that a preliminary investigation found no connection to terrorism.
The damage appears to be related to a mechanical issue, based on examination of the aircraft on the ground, the official said.
The official said a TSA representative based in Manila is assisting in the investigation.
The National Transportation Safety Board also is sending investigators, and an NTSB spokesman said the agency also does not suspect terrorism.