Oil slick spotted in hunt for MH370 as authorities prepare to launch unmanned submarine

The hunt for missing MH370 entered a new phase today when officials said they would deploy the unmanned submarine Bluefin 21 to scan the ocean floor "as soon as possible".

The "towed pinger locator", being pulled along by Australia's Ocean Shield in an attempt to trace signals from the plane's black boxes, will be taken out of the water after picking up four possible detections between April 5 and 8.

Angus Houston, who is heading the search said no signals had been heard for six days, adding: "It's time to go underwater."

Houston revealed that the Ocean Shield had last night detected an oil slick, but cautioned that it would take several days before a two-litre sample could be analysed to determine whether it was from the Malaysia Airlines jet, missing since March 8.

The Bluefin 21 sub will use sonar to create a map of the ocean floor. Houston said its deployment would not automatically "result in the detection of the aircraft", adding that the search with the submarine would be "a slow and painstaking process".