A remote-controlled mini-submarine deployed in the southern Indian Ocean to find the Malaysia Airlines plane on Monday launched its 16th mission with still no sign of wreckage of the missing aircraft.

Autonomous underwater vehicle Bluefin 21, a U.S. Navy probe equipped with side-scan sonar which is scouring the ocean floor for traces of the plane, has completed mission 15, the Joint Agency Coordination Centre (JAAC) said in a statement.

“Bluefin-21 concluded its mission 15 and was now on its next mission 16 this morning,” it said, as the search entered its 52nd day.

Bluefin-21 has focused the search on an area in the southern Indian Ocean where four acoustic signals were detected that led authorities to believe that the plane’s black box may be located there.

Hunt for the missing plane would continue on Monday with up to nine military aircrafts and 12 ships planning to assist the search operations.

“On Monday the Australian Maritime Safety Authority has planned a visual search area totalling approximately 54,921 square km. The centre of the search area lies approximately 1,667 km northwest of Perth,” the statement said.

It said so far no contacts of interest have been found.

“Bluefin-21 will continue to examine the areas adjacent to the focused underwater search area during mission 16.”

The Beijing-bound Malaysia Airlines flight MH370 -- carrying 239 people, including five Indians, an Indo-Canadian and 154 Chinese nationals -- had mysteriously vanished on March 8 after taking off from Kuala Lumpur.

The mystery of the missing plane continued to baffle aviation and security authorities who have so far not succeeded in tracking the aircraft despite deploying hi-tech radar and other gadgets.

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