UPDATE: Watch live as Malaysia prime minister holds press conference on missing plane here.
Meanwhile, Malaysia's head of investigations is denying that there is conclusive evidence of hijacking as an unidentified Malaysian government official has suggested.
"It is not conclusive. I'm heading the investigation and nobody is saying that. It's not true. We are looking at the possibility, we're looking at all possibilities. We're doing every profile of the passengers and crew but there is no firm evidence or leads so far," Azharuddin Abdul Rahman said, according to the Telegraph.
KUALA LUMPUR, Malaysia (TheBlaze/AP) -- A Malaysian government official involved in the investigation into the missing Malaysia Airlines jet is claiming it is now "conclusive" that the plane was hijacked.
The official, speaking on the condition of anonymity because he was not authorized to speak to the media, said investigators have concluded that one of the pilots or someone else with flying experience hijacked the missing jet.
The official says no motive has been established, and it is not yet clear where the plane was taken. The official said that hijacking was no longer a theory -- "It is conclusive."
The Boeing 777's communication with the ground was severed under one hour into a flight March 8 from Kuala Lumpur to Beijing. Malaysian officials have said radar data suggest it may have turned around and crossed back over the Malaysian peninsula westward after setting out toward the Chinese capital.
He said evidence that led to the conclusion included signs that the plane's communications were switched off deliberately, data regarding the flight path, and indications the plane was steered in a way to avoid detection by radar.
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.
Earlier on Friday, the Associated Press reported that “piracy and pilot suicide” were two of the main theories being investigated by officials.
The latest evidence suggests the plane didn’t experience a catastrophic incident over the South China Sea, such as an explosion, as first suspected. Since then, theories have run amok.
This story has been updated.