Media playback is unsupported on your device Media caption ACM Angus Houston: Bluefin-21 will create a 3D map of the ocean floor 
 
 Teams searching for the missing Malaysia Airlines plane are to deploy a robotic submarine for the first time. 
 
 Search chief Angus Houston said the Bluefin-21 drone would be sent down as soon as possible to search for wreckage on the sea floor. 
 
 Teams have been using a towed pinger locator to listen for signals from the plane's "black box" flight recorders. 
 
 But no new signals have been heard since 8 April, amid concerns the flight recorders' batteries have expired. 
 
 Flight MH370 went missing on 8 March with 239 people on board. It was flying from Kuala Lumpur to Beijing when it lost contact with air traffic controllers over the South China Sea. 
 
 Malaysian officials believe, based on satellite data, that it ended its flight in the southern Indian Ocean, thousands of kilometres off course. 
 
 'Manageable search area' 
 
 An international search has focused on waters west of the Australian city of Perth, with teams racing against time to detect signals before the flight recorder batteries - which last about one month - run out. 
 
 Image copyright Getty Images Image caption The Bluefin-21 will search the sea floor for wreckage from flight MH370 
 
 Image copyright Reuters Image caption Up to 12 planes and 15 ships were involved in the search for the plane 
 
 Air Chief Marshal Houston, who heads the joint agency co-ordinating the search effort, said that given no signals had been detected in six days, it was time to go underwater. 
 
 The Bluefin-21 - an almost 5m-long underwater autonomous vehicle that can create a sonar map of the sea floor - will search for wreckage in an area defined by four signals heard last week. 
 
 Officials believe those signals - picked up by the pinger locator towed by an Australian vessel - are consistent with flight recorders. 
 
 "Analysis of the four signals has allowed the provisional definition of a reduced and manageable search area on the ocean floor," ACM Houston said. 
 
 "The experts have therefore determined that the Australian Defence Vessel Ocean Shield will cease searching with the towed pinger locator later today and deploy the... Bluefin-21 as soon as possible.'' 
 
 He warned that the submersible search would be a long, "painstaking" process that might, in the end, yield no results. 
 
 Each Bluefin-21 mission will last 24 hours, with 16 hours spent on the ocean floor, four hours' diving and resurfacing time, and four hours to download data. 
 
 MH370 - Facts at a glance 8 March: Malaysia Airlines Kuala Lumpur-Beijing flight carrying 239 people disappears 
 
 Malaysia Airlines Kuala Lumpur-Beijing flight carrying 239 people disappears Plane's transponder, which communicates with ground radar, was switched off as it left Malaysian airspace 
 
 Satellite 'pings' indicate plane was still flying seven hours after satellite contact was lost 
 
 24 March: Based on new calculations, Malaysian PM says "beyond reasonable doubt" that plane crashed in southern Indian Ocean with no survivors What we know The search for flight MH370 
 
 The Ocean Shield had also spotted an oil slick in the same area where the signals had been heard, ACM Houston said, and a sample was being sent for testing. 
 
 "I stress the source of the oil is yet to be determined but the oil slick is approximately 5,500m downwind... from the vicinity of the detections picked up by the towed pinger locator," he said. 
 
 Australian officials have said previously that they are confident they are searching in the right area for the missing plane. 
 
 Officials have no idea yet why the plane diverted so far from its intended flight path. Investigators are looking at options including hijacking, mechanical failure, sabotage and pilot action. 
 
 But recovering the flight recorders is seen as key to understanding what happened to the plane. ||||| 1 of 8. The Bluefin-21 Autonomous Underwater Vehicle is craned over the side of the Australian Defence Vessel Ocean Shield in the southern Indian Ocean during the continuing search for the missing Malaysian Airlines flight MH370 in this picture released by the Australian Defence Force April 17, 2014. 
 
 PERTH, Australia (Reuters) - Footage taken by a deep-sea drone should determine sooner than previously thought whether a remote stretch of the Indian Ocean is the final resting place of a missing Malaysian jetliner, Australian search authorities said on Thursday. 
 
 After the U.S. Navy robot submarine Bluefin-21 completed its first full scan of the seabed some 2,000 km (1,240 miles) west of the Australian city of Perth, authorities said they had reduced the search area based on further analysis of what they believe may be signals from the plane's black box. 
 
 It came as an air-and-sea search was expected to be scaled down almost six weeks after Malaysia Airlines flight MH370 disappeared from radar screens mid-flight with 239 people on board. 
 
 A series of "pings" recorded this month have led searchers to the remote stretch of ocean in the belief that the signals may have come from the plane's black box recorders. 
 
 However, with no pings received in more than a week and the black box's battery now 10 days past its approximate expiry date, authorities are relying on the Bluefin drone. 
 
 On April 15, a U.S. Naval spokesman said the drone would take up to two months to search its designated area, but on Thursday the Australian Joint Agency Coordination Centre said that was now incorrect. 
 
 "Since the US Navy provided comment some days ago, the underwater search has been significantly narrowed through detailed acoustic analysis conducted on the four signal detections made by the Towed Pinger Locator," the JACC said in a statement. 
 
 The analysis had created a "reduced and more focused underwater search area". 
 
 "The current underwater search efforts are being pursued to their completion so we can either confirm or discount the area as the final resting place of MH370," the statement said. 
 
 AIRCRAFT CONTINUE TO SEARCH 
 
 Meanwhile, a separate lead in the search, a sample taken from an oil slick picked up in the area, had been analyzed and was found not to be aircraft engine oil or hydraulic fluid, the JACC said, suggesting it was not related to an aircraft. 
 
 On Monday, the search coordinator, retired Air Chief Marshal Angus Houston, said the air and surface search for debris would likely end in three days as the operation shifted its focus to the largely unmapped area of ocean floor. 
 
 However, authorities said on Thursday up to 10 military aircraft, two civil aircraft and 11 ships would still search an area totaling about 40,000 square km (15,450 square miles). 
 
 That would suggest searchers, under pressure from the families of those on board the plane, still hold some hope of finding floating wreckage. 
 
 Australian Prime Minister Tony Abbott was quoted by the Wall Street Journal on Wednesday as saying that "we believe that (underwater) search will be completed within a week or so. If we don't find wreckage, we stop, we regroup, we reconsider". 
 
 Asked by Reuters on Thursday to clarify Abbott's comments to the newspaper, his office said he was only suggesting that authorities may change the area being searched by the Bluefin-21 drone, not that the search would be called off. 
 
 Malaysia's defense minister, Hishammuddin Hussein, vowed that the search would continue even if there could be a pause to regroup and reconsider the best area to scour. 
 
 "The search will always continue. It's just a matter of approach," he told a news conference in Kuala Lumpur. 
 
 He said Abbot remained in close contact with Malaysian Prime Minister Najib Razak and the two had spoken on Thursday to discuss the search. 
 
 "They've been looking for 40 days and haven't found anything floating yet," Geoffrey Dell, Associate Professor of Accident Investigation and Forensics at Central Queensland University, told Reuters. 
 
 "You'd have to start saying there's either nothing to find or let's move elsewhere," he said. 
 
 (Additional reporting by Al-Zaquan Amer Hamzah in Kuala Lumpur; Writing by Matt Siegel; Editing by Paul Tait, Robert Birsel and Mike Collett-White) ||||| 1 of 7. A fast response craft from Australian Defence Vessel Ocean Shield tows Able Seaman Clearance Diver Michael Arnold as he searches the ocean for debris in the search zone in the southern Indian Ocean for the missing Malaysian Airlines flight MH370 in this picture released by the Australian Defence Force April 8, 2014. 
 
 SYDNEY/PERTH, Australia (Reuters) - An Australian ship which picked up possible "pings" from the black box recorders of a missing Malaysia Airlines jetliner has been unable to detect any further signals and time is running out to narrow the massive search, officials said on Tuesday. 
 
 Angus Houston, head of the Australian agency coordinating the search for Malaysia Airlines Flight MH370, said the month-long hunt in the Indian Ocean was at a critical stage given the batteries in the black box beacons had already reached the end of their 30-day expected life. 
 
 A U.S. Navy "towed pinger locator" onboard Australia's Ocean Shield picked up two signals consistent with black box locator beacons over the weekend - the first for more than two hours and the second for about 13 minutes. 
 
 Houston said the signals represented the best lead in the search yet, but efforts to pick up the pings again had so far been unsuccessful. 
 
 "If we don't get any further transmissions, we have a reasonably large search area of the bottom of the ocean to prosecute and that will take a long, long time. It's very slow, painstaking work," said Houston. 
 
 The black boxes record cockpit data and may provide answers about what happened to the plane, which was carrying 227 passengers and 12 crew when it vanished on March 8 and flew thousands of kilometers off its Kuala Lumpur-to-Beijing route. 
 
 Authorities say evidence, including the loss of communications, suggests the plane was deliberately diverted by someone familiar with the aircraft, but have not ruled out mechanical problems. 
 
 Analysis of satellite data led investigators to conclude the Boeing 777 came down in an area some 1,680 km (1,040 miles) northwest of Perth, near where possible pings were picked up and the search is now focused. 
 
 BLUEFIN ON HOLD 
 
 An autonomous underwater vehicle (AUV) named Bluefin-21 is onboard the Ocean Shield and could be sent to look for wreckage on the sea floor, but narrowing the search zone first was critical, Houston said. 
 
 "It is a large area for a small submersible that has a very narrow field of search, and of course, it is literally crawling along the bottom of the ocean," he said. 
 
 "That's why it's so important to get another transmission and we need to continue until there's absolutely no chance the (black box) device is still transmitting." 
 
 The Bluefin will scour the ocean floor in 20-hour missions using sonar in an attempt to find the aircraft, before its findings are downloaded and analyzed on board the Ocean Shield. 
 
 If anything unusual is spotted, the sonar on board the robotic vehicle will be replaced with a camera to take a closer look. The potential search area is about 4.5 km (2.8 miles) deep, the outer reach of the Bluefin's range. 
 
 Some 133 missions have been completed so far in the multinational aerial hunt for debris in the southern Indian Ocean and would continue, officials said. 
 
 Up to 11 military planes, three civilian planes and 14 ships planned to take part in the search on Tuesday, with good weather in the search area. But so far, searchers have only turned up fishing gear and other detritus. 
 
 "Even after the black box is found, the surface search will continue because they're looking for evidence to investigate why the aircraft went down," Lieutenant Commander Adam Schantz, the officer in charge of U.S. Navy P-8 Poseidon search unit, told Reuters. 
 
 "So, we'll continue for a while trying to find anything on the surface that might give a reasoning behind the accident." 
 
 (Additional reporting by Jane Wardell in Sydney and Anuradha Raghu in Kuala Lumpur; Editing by Dean Yates and Michael Perry)
– After six days with no fresh pings detected, the chief of the search for Malaysia Airlines Flight 370 says it's time to go underwater. The Bluefin-21 underwater autonomous vehicle will now be deployed to search for wreckage in an area defined by signals picked up last week that are believed to have been from the missing jet's data recorders, reports the BBC. Search chief Angus Houston says the robotic sub will be in a "reduced and manageable search area on the ocean floor" and, with the data recorders' batteries now almost certainly dead, efforts to detect pings will cease. On its first 24-hour mission, the Bluefin-21 will search an area of around 15 square miles, producing a high-resolution map of the sea floor, the Los Angeles Times reports. Houston warns, however, that the underwater search will be a "slow and painstaking process" with no guarantee of results. The area being searched, he says, is extremely deep—2.8 miles—and is largely unknown terrain "new to man." An oil slick detected on the surface of the area last night, meanwhile, is being analyzed and officials believe it didn't come from any of the search vessels, CNN reports.