A Malaysian investigation into the missing flight 370 has concluded that one or more people with flying experience switched off communications devices and deliberately steered the airliner off-course, a Malaysian government official involved in the investigation said Saturday.

The official called the disappearance a hijacking, though he said no motive has been established and no demands have been made known. It's not yet clear where the plane ended up, said the official, who spoke on condition of anonymity because he was not authorized to brief the media.

The official said a deliberate takeover of the plane was no longer a theory. "It is conclusive,'' he said, indicating that investigators were ruling out mechanical failure or pilot error in the disappearance.

He said evidence that led to the conclusion were signs that the plane's communications were switched off deliberately, data about the flight path and indications the plane was steered in a way to avoid detection by radar.

The Boeing 777's communication with the ground was severed just under one hour into a Malaysia Airlines flight March 8 from Kuala Lumpur to Beijing. Malaysian officials previously have said radar data suggest it may have turned back toward and crossed over the Malaysian peninsula after setting out on a northeastern path toward the Chinese capital.

Earlier, an American official told The Associated Press that investigators are examining the possibility of "human intervention'' in the plane's disappearance, adding it may have been ``an act of piracy.''

While other theories are still being examined, the U.S. official said key evidence suggesting human intervention is that contact with the Boeing 777's transponder stopped about a dozen minutes before a messaging system on the jet quit. Such a gap would be unlikely in the case of an in-flight catastrophe.

The Malaysian official said only a skilled aviator could navigate the plane the way it was flown after its last confirmed location over the South China Sea. The official said it had been established with a "more than 50 percent'' degree of certainty that military radar had picked up the missing plane after it dropped off civilian radar.
(AP)