The location of the black box flight recorder of the missing Malaysia Airlines flight has been narrowed down to "some kilometres", Prime Minister Tony Abbott says.
Mr Abbott told business leaders in Shanghai on Friday that although the search in the Indian Ocean was narrowing, authorities were still a long way from recovering any wreckage of MH370.
"We are confident that we know the position of the black box flight recorder to within some kilometres," Mr Abbott said.
"Still, confidence in the approximate position of the black box is not the same as recovering wreckage from almost four and a half kilometres beneath the sea or finally determining all that happened on that flight."
The prime minister was due to brief Chinese president Xi Jinping, whose country lost 154 of the 239 passengers, in Beijing on Friday afternoon.
Mr Abbott's comments, however, seemed to be contradicted by Australian search coordinator, retired Air Chief Marshal Angus Houston, who said a signal detected by an Orion aircraft on Thursday was not related to MH370's locator beacon.
"On the information I have available to me, there has been no major breakthrough in the search for MH370," Air Chief Marshal Houston said.
- AAF aircraft detects another possible signal as search area narrows
- Malaysia Airlines lost black box data in 2012
- Almost five weeks and still nothing
But the prime minister repeated his comments in a speech to business leaders after the former defence chief's statement.
This came after The West Australian aviation editor Geoffrey Thomas created a social media stir by tweeting: "Black boxes of MH370 may have been found. PM to make announcement at 11.45am [Perth time, 1.45pm AEST]."
The Australian vessel Ocean Shield has to date recorded four signals in the same search area.
But there are concerns the black box's batteries, which have a life of around 30 days, will die within days.
Saturday will mark five weeks since flight MH370 and its passengers and crew disappeared.
The Ocean Shield on Friday was in an area about 2200km northwest of Perth continuing sweeps of its pinger locator to detect further signals.
Orion aircraft were also continuing their acoustic searches.
Mr Abbott told reporters in Shanghai the area had been "very much narrowed down" by the ping detections.
"Nevertheless, we're getting to the stage where the signal from what we are very confident is the black box is starting to fade," he said.
"We are hoping to get as much information as we can before the signal finally expires."
He said Australia was determined to solve what is one of the great mysteries of modern times.
Air Chief Marshal Houston said the Ocean Shield was doing more focussed sweeps of the towed pinger locator in a bid to find further signals.
The vessel detected signals on Saturday and Tuesday in the northern end of the search zone, more than 2200 kilometres northwest of Perth.
"It is vital to glean as much information as possible while the batteries on the underwater locator beacons may still be active," Mr Houston said on Friday.
The AP-3C Orions continue their acoustic search, working in conjunction with Ocean Shield, with three more missions planned for the day.
Mr Houston said a decision as to when to deploy the autonomous underwater vehicle Bluefin-21 would be made on advice from experts on board the Ocean Shield and could be some days away.
Earlier, aviation expert Geoffrey Thomas told radio station 6PR in Perth that he had thought the black box locator may have been found.
"The Ocean Shield, which is towing the pinger, and also the HMS Echo, which is the hydrographic ship, both of them have left the search area, which is rather interesting, and they’ve also left the search area at some speed. They’re obviously no longer towing the pinger locater," Thomas said.
"At the same time we’ve heard from sources of ours in Sydney that the Prime Minister might be making an announcement ... and the suggestion is they may have triangulated and located the black boxes, but that’s unconfirmed."
New signal spurs search for missing MH370 black boxes
The logging of a fifth signal spurred Friday's hunt for missing Malaysian airliner MH370 as search crews work round-the-clock to find elusive wreckage in the southern Indian Ocean.
The Australian-led operation out of a Perth airbase is racing to gather as many signals as possible to determine an exact resting place for the Boeing 777 before sending down a submersible to plumb the depths.
The ping-emitting beacons on Flight MH370's data and cockpit voice recorders are expected to fade, more than a month after the plane vanished with 239 people on board.
With analysis of the latest ping underway, the Perth-based Joint Agency Coordination Centre (JACC) said Friday the search area had been further reduced to two zones totalling 46,713 square kilometres (18,06 square miles).
The core of the search is now 2,312 kilometres (1,436 miles) northwest of Perth.
US Seventh fleet spokesman Commander William Marks had earlier voiced optimism that the first two sets of signals showed the hunt was getting "closer and closer".
"When you put those two (sets of pings) together, it makes us very optimistic," Marks told CNN on Thursday.
"This is not something you find with commercial shipping, not something just found in nature -- this is definitely something that is man-made, consistent with what you would find with these black boxes."
Marks said he expected the pings to last "maybe another day or two" as the batteries powering the black box beacons fade after their normal lifespan of about 30 days.
- Still no debris spotted -
No floating debris from the Malaysia Airlines aircraft has yet been found, JACC said, despite the massive multinational air and sea operation.
JACC says the high-tech underwater surveillance is intended to define a reduced and more manageable search area in depths of around four kilometres (2.5 miles).
Houston has stressed the need to find the wreckage and urged repeatedly against unduly inflating hopes, for the sake of the families of missing passengers and crew who have endured a month-long nightmare punctuated by a number of false leads.
But he has voiced renewed optimism as day by day the search edges forward with new information.
No other ships are being allowed to sail near the Ocean Shield as it must work in an environment as free of noise as possible.
But JACC announced that up to 12 military aircraft, three civil aircraft and 13 ships will join Friday's hunt.
JACC says says it should not be long before a US-made autonomous underwater vehicle called a Bluefin-21 will be sent down to investigate, but has cautioned that it will have to operate at the very limits of its capability given the vast depths involved.
In Malaysia, Home Minister Zahid Hamidi said there was "no conclusive evidence yet" from the continuing investigation into what caused the plane to divert from its Kuala Lumpur-Beijing route.
Zahid said 180 people had been interviewed, including relatives of passengers and crew as well as airline ground staff and engineers.
Numerous theories have been put forward to explain MH370's baffling disappearance.
They include a hijacking or terrorist attack, a pilot gone rogue or a sudden catastrophic event that incapacitated the crew and left the plane to fly for hours until it ran out of fuel.