Australia officials said on Monday that signals picked up by a black box detector attached to an Australian ship searching for missing flight MH370 were consistent with those emitted by flight recorders.
The news came after both Chinese and Australian ships at the weekend said signals had been detected in different parts of the Indian Ocean.
“The towed pinger locator deployed from the Australian defence vessel Ocean Shield has detected signals consistent with those emitted from aircraft black boxes,” said Angus Houston, the former Australian defence chief who is leading the search coordination body, though he emphasised that further confirmation was needed.
One of the contacts lasted two hours and 20 minutes, and the second contact lasting for 13 minutes, said Houston.
"Clearly, this is a most promising lead," Houston said at a news conference in Perth.
Confirmation of whether the signals were emitted from the Malaysian plane, missing since March 8 with 239 people on board, could take several days, he said.
Australian navy ship Ocean Shield, which is carrying high-tech sound detectors from the US Navy, is investigating.
On Monday a British navy ship with sound-locating equipment arrived in a patch of ocean where the Chinese said they had picked up signals.
Searchers on Monday were anticipating good weather, with nine military planes, three civilian planes and a total of 14 ships expected to search for Flight 370, which vanished a month ago.
Three separate but fleeting sounds from deep in the Indian Ocean offered new hope yesterday in the hunt for the missing jet.
The head of the multinational search being conducted off Australia's west coast confirmed that a Chinese ship had picked up electronic pulse signals twice in a small patch of the search zone, once on Friday and again on Saturday.
Yesterday an Australian ship carrying sophisticated deep-sea sound equipment picked up a third signal in a different part of the massive search area.
"This is an important and encouraging lead, but one which I urge you to treat carefully," said Angus Houston, who is co-ordinating the search.
He stressed that the signals had not been verified as being linked to flight 370, which was travelling from Kuala Lumpur to Beijing when it disappeared on March 8 with 239 people on board.
"We have an acoustic event. The job now is to determine the significance of that event," Houston said, referring to each of the three transmissions. "There are lots of noises in the ocean, and sometimes the acoustic equipment can rebound, echo if you like."
The British navy ship HMS Echo was moving to the area where the signals were picked up by the Chinese patrol vessel Haixun 01 and would probably get there early today, Houston said.
The Australian navy's Ocean Shield would also head there, but would first investigate the sound it picked up, he said.
Speculation regarding the plane's flight path also grew after a report claimed the aircraft flew around Indonesian airspace after vanishing from Malaysian military radar.
The Boeing 777 jet might have intentionally taken a route designed to avoid radar detection, CNN quoted an unnamed senior Malaysian official as saying.
Two-thirds of the passengers aboard the missing plane were Chinese, and a group of relatives has been in Kuala Lumpur to follow the investigation.
As some families were leaving yesterday, they issued a letter requesting that the international rescue bodies that found a missing Air France jet in 2009 join the current search operation.
Additional reporting by Teddy Ng