Australian Prime Minister Tony Abbott said Saturday it will likely take a long time to locate the Malaysian passenger jet that went missing five weeks ago.
He told reporters the search area has been considerably narrowed, but trying to find anything nearly five kilometers under the surface of the Indian Ocean a thousand kilometers from land is a huge task that will likely continue for some time.
No new underwater signals were heard Saturday from the missing plane as the search continued for the black box flight data recorders.
Abbott said Saturday on the final day of his visit to China that there is still a high degree of confidence the transmissions searchers have been picking up are from Malaysia Airlines flight 370, but many difficulties remain.
FILE - A Royal Australian Air Force AP-3C Orion flies past Australian Defense vessel Ocean Shield on a mission to drop sonar buoys to assist in the acoustic search of the missing Malaysia Airline jet.
The Australian leader briefed Chinese President Xi Jinping Friday on the status of the search. Some two-thirds of the passengers onboard the flight were Chinese.
Pings consistent with a flight data recorder have been detected by an Australian ship that is using a U.S. naval device to detect black boxes.
Time is running out for authorities to locate the origin of the signals, since the batteries on the black box's locator beacon are set to run out after about 30 days.
The Malaysia Airlines jet, which was carrying 239 people, disappeared on March 8 while traveling from Kuala Lumpur to Beijing.
Malaysian authorities believe the plane was deliberately diverted and crashed into the sea. But without wreckage, many are skeptical.
If authorities can locate more pings, they plan to deploy a robot submarine to search the ocean floor.
Once the black box is retrieved, authorities believe they will be able to determine what happened to the plane. Its fate has become one of the most puzzling mysteries in aviation history.
Some information for this report provided by AP, AFP and Reuters.