Missing MH370: Robotic submarine finds 'no objects of interest'

The first mission of the robotic submarine deployed to locate the crashed Malaysian jet's wreckage today failed to detect any "objects of interest" and its search was cut short after the waters proved to be beyond its operating depth.

The autonomous underwater vehicle Bluefin 21, a US Navy probe equipped with side-scan sonar, was deployed last evening from the Australian navy ship Ocean Shield to map the floor of the Indian Ocean for the wreckage of Malaysia Airlines Flight MH370.

The mission was aborted early, sending the drone back to the surface before expected after it encountered water deeper than its operating limits of 4.5 km.

"After completing around six hours of its mission, Bluefin-21 exceeded its operating depth limit of 4,500 metres and its built in safety feature returned it to the surface," the Joint Agency Coordination Centre (JACC) which is leading the search said on the 39th day of the hunt for the plane.

Search officials analysed data from Bluefin-21, and found no objects of interest, the US Navy said today.

"To account for inconsistencies with the sea floor, the search profile is being adjusted to extend the sonar search for as long as possible," the US statement said.

"Bluefin-21 was unable to complete its first search mission after six hours, due to breaching maximum operating depth," it said.

The vehicle was recovered and six hours' worth of data downloaded.

"The data was analysed and no objects of interest were found," the statement said. "The vehicle is in good material and working condition."

The Bluefin-21 was to make a second mission to the remote Indian Ocean seabed when weather conditions permit.

Malaysia's Acting Transport Minister Hishammuddin Hussein told reporters in Kuala Lumpur that it's "not important" who gets the black box, it's more important to find the truth.

Finding the black box is crucial to know what happened on March 8 before the Beijing-bound plane with 239 people, including five Indians, an Indo-Canadian and 154 Chinese nationals, mysteriously vanished after taking off from Kuala Lumpur.

The batteries powering the black box are certified to be working for 30 days, but can still provide weak signals for some more days. Stored in a plane's tail, they are designed to begin sending off distinct, high-pitched signals as soon as they come in contact with water.

Meanwhile, Australian chief search coordinator Angus Houston said officials were investigating an oil slick about 5,500 metres from the area where the last pings were detected.

Nine military aircraft, two civilian planes and 11 ships took part in today's search operations.