It WAS hijacked: Malaysian official says it's CONCLUSIVE jet carrying 239 passengers was seized by 'someone or group with significant flying experience'

Malaysian officials confirmed missing plane was hijacked by one or several people who turned off communication system and steered it off-course, according to sources

At a press conference Saturday, Malaysian Prime Minister Najib Razak refused to confirm reports the plane was 'hijacked', but admitted that disabled communication system and flight redirection was the result of 'deliberate action' on the plane.

Investigators working to establish motive and where plane was taken if it reached end destination

PM Razak said satellite data suggests plane could have been in one of two possible corridors: northern corridor from border of Kazakhstan and Turkmenistan to northern Thailand, or southern corridor from Indonesia to the Southern Indian Ocean

Malaysian authorities have expanded their search to 27,000 square nautical miles and now focused on the west side of the Malay Peninsula and into the Indian Ocean

As of Saturday, 14 countries, 43 ships and 58 aircraft are involved in the search

Plane may have flown for about five hours after it was reported lost

The plane vanished on March 8 as it flew from Kuala Lumpur to Beijing

Authorities set to investigate the backgrounds of the 227 passengers, 10 crew and two pilots on board

Malaysia is under fire, with China describing the search effort as 'chaotic' and 'woefully inadequate'

Relatives of passengers frustrated with the lack of information

Malaysian Prime Minister Najib Razak expected to address a press conference Saturday

Malaysia also accused of having more information than they're releasing