Image copyright AFP Image caption Malaysian officials have highlighted two possible vectors they believe the plane may have flown in

Australia will take control of the "southern vector" search for the missing Malaysian plane, its PM says, as a multinational effort continues.

Malaysian officials say the plane was intentionally diverted and could have flown on either a northern or southern arc from its last known position.

More than 20 nations have been asked to help search for flight MH370, and evaluate radar and satellite data.

There has also been scrutiny of the last communication from the plane.

Malaysian officials said on Sunday that the last words from the cockpit - "All right, good night" - came after the Aircraft Communications Addressing and Reporting System (ACARS), which transmits key information about the plane to the ground, had been deliberately switched off.

On Saturday police searched the homes of Captain Zaharie Shah and co-pilot Fariq Abdul Hamid. A flight simulator taken from the captain's home was being re-assembled and examined at police headquarters, officials said.

Friends of both pilots - who investigators say did not ask to fly together - have expressed disbelief at the possibility of their involvement.

Investigators are also looking at passengers, engineers and other ground staff who may have had contact with the aircraft before take-off in their search for clues.

'One possible path'

Analysis Malaysia has now asked other countries around the region and beyond to review their radar playbacks, both primary (mainly military) and secondary (chiefly civilian). This is a region where there is growing investment in advanced defence capabilities. But there may be questions for other countries too as to whether their air defence arrangements are quite as they appear, or whether there are more gaps. The plane was apparently at one stage heading in the direction of India's Andaman and Nicobar islands. But it has been reported that military radars there might not even have been operating, as the threat level there was perceived as low. MH370 and the military gaps

The plane, carrying a total of 239 passengers and crew, left Kuala Lumpur for Beijing at 00:40 local time (16:40 GMT) on 8 March.

It disappeared off air traffic controllers' screens at about 01:20, when it was over the South China Sea.

Malaysian officials said on Saturday that according to a military radar, the aircraft then turned and flew back over Malaysia before heading in a north-west direction.

A satellite was able to pick up a signal from the plane until 08:11 local time, although it was unable to give a precise location.

Investigators are now looking at two possible corridors - a northern corridor stretching from the border of Kazakhstan and Turkmenistan through to northern Thailand, and a southern corridor stretching from Indonesia to the southern Indian Ocean.

Australian Prime Minister Tony Abbott said he was adding more resources to the search in response to a request from Malaysia.

Mr Abbott told parliament on Monday that Malaysian Prime Minister Najib Razak asked Australia to "take responsibility for the search on the southern vector, which the Malaysian authorities now think was one possible flight path for this ill-fated aircraft".

"I agreed that we would do so. I offered the Malaysian prime minister additional maritime surveillance resources which he gratefully accepted."

Malaysia's navy and air force were also deploying assets to the southern corridor on Monday, Malaysia's transport ministry said.

Meanwhile, Kazakhstan's Civil Aviation Authority said it was not possible for the plane to have reached its airspace undetected.

Senior official Serik Muhtybayev told the BBC that in order to reach Kazakhstan, the plane would have had to fly over China, India and several other countries.

Airspace monitoring systems and the anti-aircraft defence systems would have detected the plane, the official added.

Pakistan's Civil Aviation Authority said it had checked its radar recordings but "found no clue" connected to the flight.

Aside from Australia, Malaysia has sent diplomatic notes requesting assistance to 25 countries.

Three French officials involved in the search for Air France flight 447 from Rio de Janeiro to Paris, which crashed in 2009, had also arrived in Malaysia to offer their expertise, officials said.