Exclusive: Malaysia plane probe narrows on mid-air disintegration - source

“The fact that we are unable to find any debris so far appears to indicate that the aircraft is likely to have disintegrated at around 35,000 feet,” said the source, who is involved in the preliminary investigations in Malaysia.

If the plane had plunged intact from such a height, breaking up only on impact with the water, search teams would have expected to find a fairly concentrated pattern of debris, said the source, speaking on condition of anonymity because he was not authorized to speak publicly on the investigation.
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Asked about the possibility of an explosion, such as a bomb, the source said there was no evidence yet of foul play and that the aircraft could have broken up due to mechanical issues.