REPUBLIKA.CO.ID, KUALA LUMPUR - Investigators probing the disappearance of a Malaysia Airlines jetliner with 239 people on board believed it most likely flew into the southern Indian Ocean, a source close to the investigation said on Wednesday.

"The working assumption is that it went south, and furthermore that it went to the southern end of that corridor," said the source, who spoke on condition of anonymity.

The view is based on the lack of any evidence from countries along the northern corridor that the plane entered their airspace, and the failure to find any trace of wreckage in searches in the upper part of the southern corridor.

No wreckage has been found from Flight MH370, which vanished from air traffic control screens off Malaysia's east coast at 1:21 am local time on March 8 (1721 GMT March 7), less than an hour after taking off from Kuala Lumpur bound for Beijing.

An unprecedented search for the Boeing 777-200ER is under way involving 26 nations in two vast search "corridors": one arcing north overland from Laos towards the Caspian Sea, the other curving south across the Indian Ocean from west of Indonesia's Sumatra island to west of Australia.

China, which is leading the northern corridor search with Kazakhstan, said it had not yet found any sign of the aircraft crossing into its territory. Malaysian and US officials believe the aircraft was deliberately diverted perhaps thousands of miles off course, but an exhaustive background search of the passengers and crew aboard has not yielded anything that might explain why.

The minister in charge of the operation said the multinational search team was deploying the most sophisticated equipment available to find the plane.

"It probably is the largest peacetime armada of assets and satellite information-sharing that we have ever seen for a rescue and search operation," Malaysia's Acting Transport Minister Hishammuddin Hussein said.

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