Electronic pulse signals reportedly detected by a Chinese ship in the southern Indian Ocean are consistent with those of an aircraft black box, the Australian-led joint agency co-ordinating the search for the missing Malaysian jetliner said.
However, Australian Air Chief Marshal Angus Houston said that the agency cannot verify any connection between the signals and Malaysian Airlines Flight MH370.
China's Xinhua News Agency reported that a black box detector deployed by the ship, Haixun 01, picked up a signal at 37.5 kilohertz (cycles per second), the same frequency emitted by flight data recorders.
Xinhua also said a Chinese search plane spotted numerous white floating objects about 90 kilometres (56 miles) away.
Mr Houston said the joint agency has no confirmation the floating objects are related to the missing aircraft.
Military and civilian planes, ships with deep-sea searching equipment and a British nuclear submarine scoured a remote patch of the southern Indian Ocean off Australia's west coast in an increasingly urgent hunt for debris and the "black box" recorders that hold vital information about Malaysia Airlines Flight MH370's last hours.
After weeks of fruitless looking, officials face the daunting prospect that sound-emitting beacons in the flight and voice recorders will soon fall silent as their batteries die after sounding electronic "pings" for a month.
Malaysia's civil aviation chief, Azharuddin Abdul Rahman, confirmed that the frequency emitted by Flight MH370's black boxes were 37.5 kilohertz and said authorities were verifying the report.
Earlier on Saturday, Xinhua reported that a Chinese military aircraft searching for the missing aircraft spotted "white floating objects" not far from where the electronic signals were detected.
Mr Houston said the Australian-led Joint Agency Coordination Centre heading the search operation could not yet verify the Chinese reports and had asked China for "any further information that may be relevant". He said the Australian air force was considering deploying more aircraft to the area where the Chinese ship reportedly detected the sounds.
"I have been advised that a series of sounds have been detected by a Chinese ship in the search area. The characteristics reported are consistent with the aircraft black box," Mr Houston said, adding that the Australian-led agency had also received reports of the white objects sighted on the ocean surface about 90 kilometres (56 miles) from where the electronic signals were detected.
"However, there is no confirmation at this stage that the signals and the objects are related to the missing aircraft," Mr Houston said.
Still, Malaysia's defence minister and acting transport minister, Hishammuddin Hussein, was hopeful. "Another night of hope - praying hard," he tweeted in response to the latest discoveries.
There are many clicks, buzzes and other sounds in the ocean from animals, but the 37.5 kilohertz pulse was selected for underwater locator beacons on black boxes because there is nothing else in the sea that would naturally make that sound, said William Waldock, an expert on search and rescue who teaches accident investigation at Embry-Riddle Aeronautical University in Prescott, Arizona.
"They picked that (frequency) so there wouldn't be false alarms from other things in the ocean," he said.
Honeywell Aerospace, which made the boxes in the missing Malaysia Airlines plane, said the Underwater Acoustic Beacons on both the flight data recorder and cockpit voice recorder operate at a frequency of 37.5 kilohertz plus or minus 1 kilohertz.
Mr Waldock cautioned that "it's possible it could be an aberrant signal" from a nuclear submarine if there was one in the vicinity.
If the sounds can be verified, it would reduce the search area to about 10 square kilometres (four square miles), Mr Waldock said. Unmanned robot subs with sidescan sonar would then be sent into the water to try to locate the wreckage, he said.
John Goglia, a former US National Transportation Safety Board member, called the report "exciting", but cautioned that "there is an awful lot of noise in the ocean".
"One ship, one ping doesn't make a success story," he said. "It will have to be explored. I guarantee you there are other resources being moved into the area to see if it can be verified."
The Boeing 777 disappeared on March 8 while en route from Kuala Lumpur, Malaysia, to Beijing with 239 people aboard. So far, no trace of the jet has been found.
Mr Hishammuddin told reporters in Kuala Lumpur that the cost of mounting the search was immaterial compared to providing solace for the families of those on board by establishing what happened.
"I can only speak for Malaysia, and Malaysia will not stop looking for MH370," Mr Hishammuddin said.
He said an independent investigator would be appointed to lead a team that will try to determine what happened to Flight MH370. The team will include three groups: one will look at airworthiness, including maintenance, structures and systems; another will examine operations, such as flight recorders and meteorology; and a third will consider medical and human factors.
The investigation team will include officials and experts from several nations, including Australia - which as the nearest country to the search zone is currently heading the hunt - China, the United States, Britain and France, Mr Hishammuddin said.
A multinational search team is desperately trying to find debris floating in the water or faint sound signals from the data recorders that could lead them to the missing plane and unravel the mystery of its fate.
Finding floating wreckage is key to narrowing the search area, as officials can then use data on currents to backtrack to where the plane hit the water, and where the flight recorders may be.
Beacons in the black boxes emit "pings" so they can be more easily found, but the batteries last for only about a month.
Officials have said the hunt for the wreckage is among the hardest ever undertaken, and will get much harder still if the beacons fall silent before they are found.
"Where we're at right now, four weeks since this plane disappeared, we're much, much closer," said aviation expert Geoffrey Thomas, editor-in-chief of AirlineRatings.com. "But frustratingly, we're still miles away from finding it. We need to find some piece of debris on the water; we need to pick up the ping."
If it does not happen, the only hope for finding the plane may be a full survey of the Indian Ocean floor, an operation that would take years and an enormous international operation.
Mr Hishammuddin said there were no new satellite images or data that can provide new leads for searchers. The focus now is fully on the ocean search, he said.
Two ships - the Australian navy's Ocean Shield and the British HMS Echo - carrying sophisticated equipment that can hear the recorders' pings returned on Saturday to an area investigators hope is close to where the plane went down. They concede the area they have identified is a best guess.
Up to 13 military and civilian planes and nine other ships took part in the search on Saturday, the Australian agency co-ordinating the search said.
Because the US navy's pinger locator can pick up signals to a depth of 6,100 metres (20,000 feet), it should be able to hear the plane's data recorders even if they are in the deepest part of the search zone - about 5,800 metres (19,000 feet). But that is only if the locator gets within range of the black boxes - a tough task, given the size of the search area and the fact that the pinger locator must be dragged slowly through the water at just one to five knots (1mph to 6mph).
Mr Houston acknowledged the search area was essentially a best guess, and noted the time when the plane's locator beacons would shut down was "getting pretty close".
The overall search area is a 217,000-square kilometre (84,000-square mile) zone in the southern Indian Ocean, about 1,700 kilometres (1,100 miles) north west of the western Australian city of Perth.