Investigators in Malaysia are skeptical the Malaysian airliner that disappeared Saturday was the target of an attack, according to U.S. and European government sources close to the probe, according to Reuters news agency.
Neither the Malaysian agency leading the investigation nor spy agencies in the United States and Europe have ruled out the possibility that the aircraft was intentionally downed.
However, Malaysian authorities have indicated mechanical or piloting problems could be reasons for the apparent crash, the U.S. sources said.
A U.S. source said one reason Malaysian authorities are leaning away from the act of terror theory is because electronic evidence indicates the jetliner may have made a turn back towards Kuala Lumpur before it disappeared.
Vietnamese military personnel take part in the search for a missing Malaysian airliner off Vietnam's Tho Chu island, March 10, 2014.
The search for flight MH370 is in its third day and the chief Malaysian investigator called its disappearance an "unprecedented mystery".
The plane vanished from radar Saturday morning about an hour after it took off from Kuala Lumpur en route to Beijing.
Azharuddin Abdul Rahman said the search area will be significantly expanded Tuesday after days of looking with no sign of the missing plane.
Dozens of ships and planes from several countries have been searching within a 92 kilometer radius from the point where the plane disappeared over the South China Sea.
Interpol confirmed at least two passengers on the flight used stolen passports and authorities are checking to see whether others aboard used false identity documents.
The Associated Press reports that authorities questioned travel agents Monday at a beach resort in Thailand about the two men, part of a growing international investigation into what they were doing on the flight.
AP also reported that five passengers who checked in for Flight MH370 didn't board the plane, and their luggage was removed from it, Malaysian authorities said. Malaysian Transport Minister Hishammuddin Hussein said this also was being investigated, but he didn't say whether this was suspicious, according to the AP report.
A senior source involved in preliminary investigations in Malaysia said the failure to find any debris indicated the plane may have broken up mid-flight, which could disperse wreckage over a very wide area.
A U.S. government source said the United States has reviewed imagery taken by American spy satellites for evidence of a mid-air explosion, but saw none.
China urged Malaysia to step up the search for the missing plane and has sent security agents to help with the investigation into the misuse of passports. More than 150 Chinese nationals were on the flight. China has sent four search-and-rescue vessels and two warships to help in the mission.
In all, eight countries joined the search for the plane early Saturday, but so far no positive sightings of the jetliner have been made. Malaysia’s Department of Civil Aviation said the eight nations have a combined 40 ships and 34 aircraft involved in the hunt.
Vietnam dispatched two planes and seven ships to search for the plane, the Ministry of Foreign Affairs said in a statement Monday. The National Committee for Search and Rescue said another five planes and four ships are on standby for search activities.Committee for Search and Rescue said another five planes and four ships are on standby for search activities.
“The wreckage is very unlikely to show up on radar, and it is also very unlikely to show in infra red, because it has the same temperature as the surface," said Greg Waldron, Asia managing editor of Flightglobal
, a trade publication for the aviation sector. "So in terms of finding pieces of the aircraft, if indeed these pieces of aircraft are floating around in the sea, you are really relying on people's eyeballs. And also the wreckage if there is wreckage has had days to spread. And this could make it more challenging to locate."
The United States sent the USS Pinckney
, an Arleigh Burke-class guided-missile destroyer, to the area on Sunday. Another vessel is on its way, according to Bleu Moore, spokesman from the 7th Fleet public affairs office.
Some information in this report was contributed by VOA's Marianne Brown and Reuters.