The head of the multinational search being conducted off Australia's west coast confirmed that a Chinese ship had picked up electronic pulsing signals twice in a small patch of the search zone, once on Friday and again on Saturday.
On Sunday, an Australian ship carrying sophisticated deep-sea sound equipment picked up a third signal in 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,'' retired Australian Air Chief Marshall Angus Houston, who is coordinating the search, told reporters in Perth.
He stressed the signals had not been verified as linked to Malaysia Airlines 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. It does not confirm or deny the presence of the aircraft locator on the bottom of the ocean,'' Houston said, referring to each of the three transmissions.
China's official Xinhua News Agency reported late Saturday that the patrol vessel Haixun 01 on Friday detected a ``pulse signal'' at 37.5 kilohertz (cycles per second) _ the same frequency emitted by flight data recorders aboard the missing plane _ in the southern Indian Ocean.
Houston confirmed the report, and said that the Haixun 01 detected a signal again on Saturday within 2 kilometers (1.4 miles) of the original signal, for 90 seconds. He said that China also reported seeing white objects floating in the sea in the area.
Houston said the British navy's HMS Echo, which is fitted with sophisticated sound locating equipment, was moving immediately to the area where the signals were picked up, and would be there in the next day or two.
The Australian navy's Ocean Shield, which is carrying high-tech sound detectors from the US Navy, will also head there, but would first investigate the sound it picked up in its current region, about 300 nautical miles (555 kilometers) away, he said.
He said Australian air force assets were also being deployed on Sunday into the Haixun 01's area to try to confirm or discount the signals relevance to the search.
After weeks of fruitless looking, the multinational search team is racing against time to find the sound-emitting beacons and cockpit voice recorders that could help unravel the mystery of the plane. The beacons in the black boxes emit ``pings'' so they can be more easily found, but the batteries only last for about a month.
Investigators believe Flight 370 veered way off course and came down somewhere in the southern Indian Ocean, though they have not been able to explain why it did so.
The Chinese crew reportedly picked up the signals using a hand-held sonar device called a hydrophone dangled over the side of a small runabout _ something experts said was technically possible but extremely unlikely.
The equipment aboard the Ocean Shield and the HMS Echo are dragged slowly behind each ship over long distances and are considered far more sophisticated than those the Chinese crew was using.
Footage aired on China's state-run CCTV showed crew members in the small boat with a device shaped like a large soup can attached to a pole. It was hooked up by cords to electronic equipment in a padded suitcase as they poked the device into the water.
If the Chinese have discovered this, they have found a new way of finding a needle in a haystack,'' said aviation expert Geoffrey Thomas, editor-in-chief of AirlineRatings.com. ``Because this is amazing. And if it proves to be correct, it's an extraordinarily lucky break.'