Nine vessels, including China's largest rescue ship Haixun 01, will sail off from Singapore to waters southeast of the Bay of Bengal and west of Indonesia, covering an area of 300,000 sq km, said the national maritime search and rescue centre.

 

 Efforts will focus on waters near Sumatra away from regions being searched by other countries, said Zhuo Li, vice director of the centre. According to the plan, four vessels heading north will pass through Strait of Malacca to reach the Bay of Bengal, while five others will travel south passing the Sunda Strait.

 

 The newly-added search areas were decided based on the two possible flight directions made by the jetliner as the Malaysian government announced.

 

 The expanded search areas — almost as large as Australia — encompass a northern corridor stretching approximately from the border of Kazakhstan and Turkmenistan to northern Thailand, and a southern one from Indonesia to the southern Indian Ocean.

 

 China's navy spokesperson Liang Yang said the country's naval vessels on standby in the Gulf of Thailand headed north of the Singapore Strait Monday evening and divided into two groups Tuesday noon.

 

 The Jinggangshan amphibious docking vessel led a fleet through the Malacca Strait and into waters west of the Andaman Islands. Another fleet consisting of supply ship Qiandaohu, missile destroyer Haikou and  amphibious transport dock Kunlunshan was heading for waters southwest of the Sumatra through the Sunda Strait, Liang said.

 

 He noted the search faced difficulties. The depth of the sea exceeds 4,000 metres and the reflection from the seabed interferes with sonar. Liang said that the navy would reinforce communication with authorities and keep adjusting the search.

 

 At Kuala Lumpur, Chinese ambassador to Malaysia Huang Huikang said  Tuesday that background checks on all passengers from the Chinese mainland on board the missing flight had found no evidence of links to sabotage or terrorism. Those passengers could now be cleared of suspicion in principle, he said.

 

 By Tuesday, 26 countries were searching for the plane, compared with 14 last week. But the multinational search has failed to determine the jetliner's whereabouts so far, and what happened to the plane remains a mystery.

 

 The plane went missing on its way to Beijing March 8, carrying 227 passengers and 12 crew.