Search crews worked Saturday to capture any final pings from the data recorder thought to belong to the missing Malaysian jet as the signals slowly faded, Australian Prime Minister Tony Abbott said on the final day of his trip to China.
Abbott said the signals, critical in narrowing the search area, were "rapidly failing" and high-tech detection instruments had captured no new pings since Tuesday. The batteries in the data recorder are designed to last about a month.
Triangulation of the four pings captured so far had narrowed the search area to 500 square miles in the southern Indian Ocean, a swath of seabed the size of Los Angeles and nearly 3 miles deep.
With those parameters, Abbott said, the search is a "massive, massive task" that is likely to take a long time. Abbott said, however, that he remained confident that the signals did come from the "black box" data recorder belonging to the Malaysia Airlines Flight 370 that disappeared en route from Kuala Lumpur to Beijing on March 8 with 239 people aboard.
"No one should underestimate the difficulties of the task still ahead of us," he said.
A U.S. Navy ping locator towed by the Australian ship Ocean Shield detected two signals a week ago and another two on Tuesday.
After the searchers narrow down the data recorder's location as much as possible, they will send a slow-moving robotic submersible, the Bluefin 21, to probe for the wreckage. It could take up to two months for the device to search the current, 500-mile zone.
Contributing: The Associated Press