Radar signals show a Malaysia Airlines plane that has been missing for more than 24 hours may have turned back, Malaysian officials have said.
Rescue teams looking for the plane have now widened their search area.
Investigators are also checking CCTV footage of two passengers who are believed to have boarded the plane using stolen passports.
Flight MH370 from Kuala Lumpur to Beijing disappeared south of Vietnam with 239 people on board.
Air and sea rescue teams have been searching an area of the South China Sea south of Vietnam for more than 24 hours.
But Malaysia’s civil aviation chief, Azharuddin Abdul Rahman, told a press conference in Kuala Lumpur the search area had been expanded, to include the west coast of Malaysia.
Five passengers booked on the flight did not board, he added. Their luggage was consequently removed.
Twenty-two aircraft and 40 ships are now involved in the search, armed forces chief Gen Zulkefli Zin said.
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.
Vietnamese navy ships which reached two oil slicks spotted earlier in the South China Sea found no signs of wreckage.
‘Suspect’
Malaysia’s Transport Minister, Hishammuddin Hussein, initially said at least four names on the passenger list were “suspect” but later told the BBC there were in fact only two suspect names.
The BBC has confirmed that 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.
