US law enforcement and intelligence officials say there is "no sign" that a bomb caused the gaping hole in the fuselage of a Qantas Airlines 747 early today over the Pacific.
Passengers heard a large "bang" as a portion of the plane's lower body blew out.
The "preliminary read out," according to ABC News correspondent Lisa Stark is that there the accident is not connected to terrorism.
A senior government official provided similar guidance.
A US official from the Transportation Security Administration, the TSA, based in the Philippines, where the plane made an emergency landing, is working with local authorities.
Alarms were raised initially because of previous al Qaeda attempts to blow up commercial jetliners over the Pacific.
Philippine Airlines flight 434 was targeted in December, 1994 for an ambitious al Queida attempt to blow up multiple jumbo jets, an operation code-named "Bojinko."