Searchers hunting for the missing Malaysia Airlines jet were racing to a patch of the southern Indian Ocean on Sunday to determine whether a few brief sounds picked up by underwater equipment came from the plane's black boxes, whose battery-operated beacons are on the verge of dying out.
Ships scouring a remote stretch of water for the plane that vanished nearly a month ago detected three separate sounds over the course of three days. A Chinese ship picked up an electronic pulsing signal on Friday and again on Saturday in a small part of the search zone, and an Australian ship carrying sophisticated deep-sea sound equipment picked up a signal in a different area on Sunday, the head of the multinational search said.
But there were questions about whether any of the sounds were the breakthrough searchers are desperately seeking or just another dead end in a hunt seemingly full of them, with experts expressing doubt that the equipment aboard the Chinese ship was capable of picking up signals from the plane's two black boxes.
``This is an important and encouraging lead, but one which I urge you to treat carefully,'' retired Australian Air Chief Marshall Angus Houston, who is coordinating the search, told reporters in Perth.
``What we've got here are fleeting, fleeting acoustic events. ... That's all we've got,'' he said. ``It's not a continuous transmission. If you get close to the device, we should be receiving it for a longer period of time than just a fleeting encounter.''
None of the signals has been verified as being linked to Flight 370, which was traveling from Kuala Lumpur, Malaysia, to Beijing when it vanished March 8 with 239 people on board.
``We are dealing with very deep water, we are dealing with an environment where sometimes you can get false indications,'' Houston said. ``There are lots of noises in the ocean, and sometimes the acoustic equipment can rebound, echo if you like.''
China's official Xinhua News Agency reported Saturday that the patrol vessel Haixun 01 detected a ``pulse signal'' Friday in the southern Indian Ocean at 37.5 kilohertz _ the same frequency emitted by the missing plane's black boxes.
Houston confirmed the report, and said the Haixun 01 detected a signal again on Saturday within 2 kilometers (1.4 miles) of the original signal, for 90 seconds. He said China also reported seeing white objects floating in the sea