PERTH, Australia - With the Malaysian jetliner mystery now five weeks old, officials have narrowed the search zone for the missing plane and are "very confident" the underwater signals they have heard are from its black box, Australia's prime minister said Friday.
At the same time, however, those electronic signals are fading, Tony Abbott added.
On a visit to China, Abbott briefed President Xi Jinping on the search for Flight 370, which vanished March 8 while flying from Kuala Lumpur, Malaysia, to Beijing carrying 239 people, most of them Chinese. Based on an analysis of satellite data, officials believe the Boeing 777 flew off course for an unknown reason and went down in the southern Indian Ocean off the west coast of Australia.
Crews involved in the hunt have in recent days focused on a more-targeted area in the ocean for the source of the electronic signals, Abbott said.
Search crews are racing against time because the batteries powering the recorders' locator beacons last only about a month - and more than a month has passed since the plane disappeared. Finding the devices after the batteries fail would be extremely difficult because the water in the area is 15,000 feet deep.
The Australian ship Ocean Shield is towing a U.S. Navy device that detects signals from flight recorders. Two sounds heard Saturday were determined to be consistent with signals emitted from the black boxes. Two more sounds were detected in the same general area Tuesday.
"We are confident that we know the position of the black box flight recorder to within some kilometers," Abbott said. "But confidence in the approximate position of the black box is not the same as recovering wreckage from almost 4-1/2 kilometers beneath the sea or finally determining all that happened on that flight."