Media playback is unsupported on your device Media caption Air Chief Marshal Angus Houston: "Until we stop the pinger search, we will not deploy the submersible" 
 
 An Australian vessel searching for the missing Malaysia Airlines plane has detected signals consistent with those from "black box" flight recorders. 
 
 The Ocean Shield ship picked up the signal twice, once for more than two hours, said Angus Houston, a retired air chief marshal leading the search. 
 
 He called it the "most promising lead" so far. 
 
 But he said more information was needed: "We haven't found the aircraft yet and we need further confirmation." 
 
 Malaysia's acting transport minister, Hishammuddin Hussein, said he had been briefed by Air Chief Marshal Houston and was "cautiously hopeful that there will be a positive development in the next few days if not hours". 
 
 The plane, carrying 239 people, was flying from Kuala Lumpur to Beijing on 8 March when it disappeared. Malaysian officials say they believe it crashed in the southern Indian Ocean. 
 
 'Two distinct returns' 
 
 ACM Houston said the signals were detected using the towed pinger locator deployed on the Ocean Shield. 
 
 Image copyright Reuters Image caption The signals were heard by the towed pinger locator deployed by the Ocean Shield 
 
 Two separate detections occurred, he said. The first was held for two hours and 20 minutes before being lost. 
 
 Analysis "Lottery odds" is how one oceanographer described to me how incredible it would be if they had actually stumbled over distress signals from the black boxes. This listening equipment trickles along at just a few miles an hour and they were searching an area the size of Britain. Now they are racing against the clock to try to pick up the signals again so they can pinpoint a better location, and send a drone down to look for parts of the aircraft. The battery on this pinger will be starting to go flat, which cuts the range. One very interesting part of these findings is the fact that they seemed to hear two separate pings on one of their sweeps. There are two pingers on board the plane, one for each black box. Could the noise be something else? Well, the frequency of black box pings, 37.5 kHz, is designed to be unique in the water. It's an unusual frequency, so that it's easier to find. But the ocean's an incredibly noisy place and people and equipment can make mistakes. 
 
 The ship then turned around and on the return leg detected the signal again for 13 minutes. 
 
 "On this occasion two distinct pinger returns were audible. Significantly this would be consistent with transmissions from both the flight data recorder and the cockpit voice recorder," ACM Houston said. 
 
 "I'm much more optimistic than I was a week ago," he said. 
 
 "We are now in a very well defined search area, which hopefully will eventually yield the information that we need to say that [Malaysia Airlines flight] MH370 might have entered the water just here." 
 
 The Ocean Shield was still in the area, about 1,040 miles (1,680 km) north-west of the Australian city of Perth, but had not been able to reacquire the signals since, he said. 
 
 The position of the signals needed to be fixed, ACM Houston said. Once that happened, the Ocean Shield could lower the Bluefin 21 underwater autonomous vehicle to try to locate wreckage on the sea floor. 
 
 The signal had been heard in sea with a depth of 4,500m, he added, which was at the limit of the capability of the Bluefin 21. 
 
 He cautioned that the next steps would take time. 
 
 "It could take some days before the information is available to establish whether these detections can be confirmed as being from MH370," he said. "In very deep oceanic water, nothing happens fast." 
 
 The search operation is in a race against time as the flight recorders' batteries are due to run out, meaning a signal would no longer be emitted. 
 
 A Chinese search vessel, Haixun 01, also said it briefly heard signals over the weekend in a different search area. 
 
 Media playback is unsupported on your device Media caption Navy divers searched the area near the signal - courtesy Australian Defence Force 
 
 Media playback is unsupported on your device Media caption Families hold a candle-lit vigil in Kuala Lumpur, as the "black box" hunt continues 
 
 Those signals are now being investigated with the help of a British naval vessel, HMS Echo, which is equipped with sophisticated sound-locating equipment. 
 
 Reports said the crew of the Chinese ship had been using a sonar device called a hydrophone to pick up sounds. 
 
 Experts said it was technically possible but unlikely that the sounds heard with this equipment related to the missing plane. 
 
 Chris Portale, a director of the US company Dukane which makes the device that emits signals from flight recorders, said looking for the Malaysian plane's "black boxes" was like "looking for a suitcase on the side of a mountain" but under water. 
 
 But he said he thought searchers were now in the right area and had a "very good hope" of spotting debris, if the signal was from the aircraft. 
 
 "I believe they have got three to four more days of good, solid output [from the flight recorders]," he told the BBC's Today Programme. 
 
 Media playback is unsupported on your device Media caption Richard Westcott reports on the use of a pinger locator to find a black box 
 
 So far, not a single piece of wreckage has been found from the missing plane, but officials have concluded - based on satellite data - that it ended its flight in the sea to the west of Perth. 
 
 Officials do not know why it lost contact with air traffic controllers and ended up so far from its intended path. 
 
 The backgrounds of both passengers and crew have been investigated but to date officials are not thought to have discovered any concrete evidence about what might have caused the plane to disappear. ||||| An Australian ship scouring the Indian Ocean for missing flight MH370 has detected two further pings consistent with the plane's two black boxes, in a "great lead", bolstering hopes for wreckage discovery. 
 
 The Australian Defence Vessel Ocean Shield, towing a US pinger locator, detected two sets of pings, on Tuesday afternoon and then again about five hours later. 
 
 The signal detected on Tuesday afternoon was held for about five minutes and 32 seconds; followed by a second signal on Tuesday night, which was held for seven minutes. 
 
 The Australian vessel Ocean Shield is towing a pinger locator in the search for MH370. Photo: AP 
 
 The development came more than two days after Ocean Shield first detected the month-long search's most promising lead: two acoustic events on Saturday. 
 
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 Retired air chief marshal Angus Houston, the head of the search's Joint Agency Co-ordination centre, announced the "promising" development during a press conference in Perth on Wednesday afternoon. 
 
 It revives hope the missing Malaysia Airlines plane's black box is still transmitting data days after its batteries were due to run dead. 
 
 Crew on the Ocean Shield deploy the towed pinger locator. Photo: AP 
 
 Mr Houston said expert data analysis on previously detected signals had found they were not of natural origin, further boosting hopes of a breakthrough. 
 
 Mr Houston said experts believed the signals were consistent with those of a flight data recorder. 
 
 He said the first two pings - detected on April 5 at 4.45pm and at 9.27pm Perth time - had been analysed by the Australasian Joint Acoustic Analysis Centre, based at HMAS Albatross in Nowra, on the NSW south coast. 
 
 "The analysis determined that a very stable, distinct and clear signal was detected at 33.331 kilohertz, and that it consistently pulsed at a 1.106-second interval," Mr Houston said. 
 
 ''They therefore asses that the transmission was not of natural origin, and was likely sourced from specific electronic equipment. They believe the signals to be consistent with the specification and description of a flight data recorder.'' 
 
 He said two latest pings were detected on Tuesday - at 4.27pm and 10.17pm, Perth time. 
 
 Mr Houston said up to 11 military aircraft, four civil aircraft and up to 14 ships would assist in Wednesday's search, while the Ocean Shield would also conduct a sonar voice search. 
 
 The search area has been refined to a single zone, about 75,423 square kilometres in size, 2261 kilometres north west of Perth, which was a considerably smaller area than in previous days, he said. 
 
 ''Based on Ocean Shield's detections, we are now searching a much more concentrated area, based on the drift predications made possible by Ocean Shield's detections,'' Mr Houston said. 
 
 ''The smaller area has also allowed us to plan much tighter search patterns based entirely on visual search principles. In other words, we have intensified our search in the visual search area. 
 
 "There's no second chances," he said. 
 
 "It looks like the signals we picked up recently have been much weaker than the original signals we picked up ... we're either a long away from it or in my view more likely the batteries are starting to fade." 
 
 Although authorities have previously said the autonomous underwater vehicle Bluefin-21 would be dropped to the ocean floor once they received a third ping, they have yet to deploy the asset. 
 
 "By triangulating this data we will be able to come up with a much smaller search area under water," Mr Houston said. 
 
 "Time spent on the surface, we're covering six times more area than we would be able to do when we get under water. With the batteries due to fail shortly, we need to get as much positional data as we can." 
 
 An RAAF aircraft has been diverted to Ocean Shield to drop buoys around the field to lay a "sonar buoy pattern", which will involve underwater and floating components transmitting data back to the aircraft. 
 
 "That will provide a range of sensors, 1000 feet down, which is 1000 feet closer to the pinger locator on the ocean floor," Commodore Leavy, the operational head of the Australian search, said. 
 
 The Malaysia Airlines Boeing 777 vanished without a trace during en route to Beijing from Kuala Lumpur on March 8. 
 
 Despite an extensive and costly international search operation off the West Australian coast, the effort has failed to turn up a single piece of evidence to confirm the plane's final resting place.
– Australian officials have sounded a fresh note of confidence in the search for Malaysia Airlines Flight 370, saying they've reacquired underwater signals following a lapse into silence. Search chief Angus Houston says an Australian navy vessel detected two sets of pings yesterday in the same area that signals were detected over the weekend, reports the Sydney Morning Herald. "I'm now optimistic that we will find the aircraft, or what is left of the aircraft, in the not too distant future—but we haven't found it yet, because this is a very challenging business," Houston told reporters. The signals are getting weaker, which could be a sign that searchers are getting further away, or, more likely, a sign that the data recorder batteries are starting to fade, explained Houston. He says they have delayed deploying the autonomous underwater vehicle Bluefin-21 to search for wreckage because with time running out, they don't want anything to get in the way of the signals. In another promising development, authorities have analyzed the pings detected over the weekend and confirmed that they came from electronic equipment, with signals consistent with those of flight data recorders, CNN reports.