Terrorism is a line of inquiry in the investigation into the sudden disappearance of a passenger jet over the seas off Vietnam.
Four passengers are under investigation say Malaysian officials, who are liaising with the FBI - stolen passports were used by two individuals to board the plane.
The Malaysia Airlines Boeing 777-200 was flying from Kuala Lumpur to Beijing when it vanished around two hours into the flight on Saturday.
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Malaysia Airlines Flight Disaster In Pictures
It was carrying 239 people, all of whom are feared dead.
No mayday warning was issued by the crew.
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.
Radar evidence shows the plane may have tried to turn back before contact was lost prompting an increase in the areas being searched for wreckage.
So far none has been found but two oil slicks consistent with a downed aircraft have been found.
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.
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.
The massive search operation consists of 22 aircraft and 40 ships.
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".