Robotic sub makes another attempt to locate MH370

A robotic mini-submarine deployed to unprecedented depths to scour a remote stretch of the Indian Ocean floor to find the missing Malaysian plane on Saturday embarked on its seventh mission with still no sign of wreckage.

Autonomous underwater vehicle Bluefin 21, a US Navy probe equipped with side-scan sonar, 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.

"Bluefin-21 AUV's seventh mission has commenced," the Perth-based Joint Agency Coordination Centre said in a statement, as the search entered into the 43rd day.

The statement said that overnight the drone completed mission six in the underwater search area.

"Bluefin-21 has searched approximately 133 square kilometres to date. Data from the sixth mission is currently under analysis. No contacts of interest have been found to date," it added.

Up to 11 military aircraft and 12 ships will assist in Saturday’s search for missing Malaysia Airlines flight MH370.

"Today the Australian Maritime Safety Authority has planned a visual search area totalling approximately 50,200 square kilometres, across three areas," the statement said.

The authorities, increasingly reliant on the $4 million Bluefin-21, have adjusted the mechanism and sent it as deep as 4,695 meters (15,403 feet), a record.

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.

Meanwhile, the Australian authorities have said the drone is expected to finish searching a narrowed down area of the Indian Ocean seabed within the next week.

Malaysia's Acting Transport Minister Hishammuddin Hussein has vowed not to back down from searching for the missing jet.

He said there was no reason to call off the search as it took two years for a remotely operated vehicle to retrieve the flight data recorders of crashed Air France flight 447 from the bottom of the Atlantic Ocean in 2011.

"We will continue no matter what approach we use (to locate the missing aircraft)," he said on Thursday.

He said any decision made concerning the search and recovery effort would take into consideration the views of the international team of investigators, via joint discussions.