Nearly 240 people are feared dead after a passenger plane reportedly crashed into the sea off Vietnam.
The Malaysia Airlines Boeing 777-200 was flying from Kuala Lumpur to Beijing when it vanished around two hours into the flight.
US officials told NBC News they have not ruled out terrorism after it was discovered two passengers were travelling on stolen passports.
The passenger manifest issued by the airline included the names of two Europeans - Austrian Christian Kozel and Italian Luigi Maraldi - who, according to their foreign ministries, were not in fact on the plane.
More information began to emerge about some of the victims aboard the doomed plane after Malaysian Airlines released a full list of the passengers on board - including five children aged two to four years old.
Passengers were from 14 countries, including 152 from China, 38 from Malaysia, six Australians and four Americans. It is believed no Britons were on board.
Earlier today, two oil slicks were spotted by the Vietnamese air force, as a major search and rescue operation was launched when the aircraft disappeared shortly after losing contact with air traffic controllers.
The two parallel slicks - both between 10 miles (16km) and 12 miles (19km) long and 500 metres apart - were seen by two Vietnamese air force jets off the south coast of Vietnam.
A Vietnamese government statement said they were consistent with the kind of spills caused by fuel from a crashed airliner.
The US Navy is helping teams from Vietnam, Malaysia and Singapore search the vast waters in the Gulf of Thailand, between Malaysia and Vietnam.
A leading aviation safety expert has said it is "extraordinary" that the pilots of a missing Malaysia Airlines plane carrying 239 people did not make a distress call.
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The Boeing B777-200 aircraft would have been cruising at about 35,000 feet when it lost contact over the South China Sea, giving the pilots "plenty of time" to report any technical problems, Flight Global's operations and safety editor David Learmount said.
Mr Learmount said: "Something happened and the pilots did not tell anyone. Why? It's a good question.
"It's extraordinary the pilots failed to call because they had plenty of time to. Unless there was a bomb on board but there has been no evidence of that."
Malaysia Airlines has now released a press statement urging people around the world to pray for flight MH370.
"It has been more than 24 hours since we last heard from MH370 at 1.30 am," it read.
"The search and rescue team is yet to determine the whereabouts of the Boeing 777-200 aircraft.
"At this stage, [search and rescue] have failed to find evidence of any wreckage. The sea mission
will continue overnight while the air mission will recommence at daylight."
The statement follows reports of family members of those on board becoming increasingly distressed due to the lack of information they have been receiving.
Reporters at the scene have spoken of "scenes of considerable distress" and "increasing irritation".
Describing the scene inside the room where some 500 relatives are waiting for news, one woman said: "They used a bus to bring us here, in this hotel. They only give us bread, biscuits and water, that's all.
"There is nobody from the airline, not even one person. Every time I ask 'where is the airline staff; what's the latest?' They say, 'we are only volunteers, we're hotel staff, we're not from the airline'."