BEIJING, April 6 (Xinhua) -- China's search vessels still failed to find any confirmed clues to the fate of the Malaysian flight MH370, now missing for 30 days, an official said Sunday.

Vessels of China's ministry of transport searching for the missing passenger jet have searched a total of 136,000 square kilometers by midday of Sunday, according to Zhuo Li, an official with the China Maritime Search and Rescue Center.

By midday Sunday, the center had mobilized 62 merchant ships for their assistance in the search, he said.

Haixun 01 of the ministry and Navy vessels 999 and 998 continued the underwater search in southern Indian Ocean, Nanhaijiu 115, Donghaijiu 101 and Navy vessel 171 were searching on the water surface, while Nanhaijiu 101 and Navy vessel 863 were searching in eastern Indian Ocean, Zhuo said.

China has made all-out efforts to search the missing plane using 18 vessels, eight helicopters and three fixed-wing aircraft.