Officials say they still have no idea what went wrong with the aircraft.

None of the debris and oil slicks spotted in the water so far have proved to be linked to the disappearance.

Four areas of investigation were focused on the possibility of human agency, the police chief said: hijacking, sabotage, psychological problems or personal problems with passengers or crew.

The passengers on the flight were of 14 different nationalities. Two-thirds were from China, while others were from elsewhere in Asia, North America and Europe.

At least 40 ships and 34 aircraft are taking part in the search in the seas off Vietnam and Malaysia.

Search teams from Australia, China, Thailand, Indonesia, Singapore, Vietnam, Philippines, New Zealand and the United States of America are assisting.

Malaysian civil aviation chief Azharuddin Abdul Rahman said the search was being conducted "on both sides" of the peninsula.

The area has been expanded from 50 nautical miles from where the plane had disappeared - over waters between Malaysia and Vietnam - to 100 nautical miles (115 miles; 185km)

据英国广播公司（BBC）报道，马来西亚警方3月11日称，持窃取护照乘坐MH370班机乘客是一名伊朗青年男子，与恐怖分子没有任何联系。

马来西亚警方表示，这位19岁的伊朗男子名叫Pouria Nour Mohammad Mehrdad，可能是想偷渡到德国去。

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