A terrorist attack or a terrible accident?
Malaysia authorities say they are now investigating four passengers believed to have travelled on false passports.
The passengers being checked had all bought their tickets through China Southern Airlines, according to a security official.
It comes amid increasing fears that all 239 people on board a Malaysia Airlines jet perished when it supposedly crashed into the South China Sea on Saturday, en route from Kuala Lumpur to Beijing.
Multinational search and rescue ships have begun combing a larger area for any sign of wreckage of the plane which went missing 40 minutes after taking off.
Azaharudin Abdul Rahman, chief of Malaysia’s Civil Aviation Authority, said: “So far there is no report of any sightings. We have extended our area of operations which includes the west side of Malaysia.”
Malaysian investigators are now working with their counterparts in America’s FBI and focusing on the entire passenger manifest, with at least two people believed to have travelled on stolen Italian and Austrian documents.
The majority of the passengers are from China. Others are from elsewhere in Asia, North America and Europe.
Mystery also surrounds the fact that no distress call appears to have been sent and that the plane vanished at cruising altitude in clear skies, one of the rarest kinds of aviation disaster.