Missing Malaysia Airlines Plane â€˜Turned Backâ€™
Air force chief Rodzali Daud said the investigation was now focusing on a recording of radar signals that showed there was a "possibility" the aircraft had turned back from its flight path.
The plane vanished at 17:30 GMT Friday.
Malaysian officials have said Flight MH370 from Kuala Lumpur to Beijing disappeared south of Vietnam with 239 people on board.
Malaysian Airlines had previously said it last had contact with air traffic controllers 120 nautical miles off the east coast of the Malaysian town of Kota Bharu.
Air and sea rescue teams have been searching an area of the South China Sea south of Vietnam for more than 24 hours.
Investigators are checking CCTV footage of two passengers who are believed to have boarded the plane using stolen passports.
A man falsely using an Italian passport and a man falsely using an Austrian passport purchased tickets at the same time, and were both booked on the same onward flight from Beijing to Europe on Saturday.
Both had purchased their tickets from China Southern Airlines, which shared the flight with Malaysia Airlines, and they had consecutive ticket numbers.
The real owners reportedly had their passports stolen in Thailand in recent years.
International agencies including the FBI have joined the investigation and all angles are being examined.
The passengers on the flight were of 14 different nationalities.
Two-thirds were from China, while others were from elsewhere in Asia, North America and Europe.
Distraught relatives and loved ones of those on board are being given assistance at both the arrival and departure airports.
Many have expressed anger at the lack of information.
The aerial search was suspended overnight but resumed on Sunday morning.
Malaysia's national carrier is one of Asia's largest, flying nearly 37,000 passengers daily to some 80 destinations worldwide.
By Angel Mboya
Source: BBC News
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