Signals believed to be from the black box data recorders of crashed AirAsia Flight 8501 were detected on Friday, Indonesian authorities said, offering the strongest lead to explain the disaster.
"A ship detected the pings. The divers are trying to reach it," said SB Supriyadi, a director with the National Search and Agency who is stationed at the search headquarters of Pangkalan Bun.
"The location of the ping is reported to be near where the tail was found."
The plane crashed into the Java Sea on December 28 during stormy weather as it flew from the Indonesian city of Surabaya to Singapore, claiming the lives of all 162 people on board.
Rough seas and strong currents have slowed multinational efforts to find the wreckage of the plane in relatively shallow waters and determine why it crashed.
The black boxes are regarded as crucial to explaining the cause of the disaster, as they should contain recordings of the pilots' final words and general flight data.
They are designed to give a ping signal for 30 days after a crash so that the recorders can be found.
The tail of the plane, where the black boxes were housed, was discovered on Wednesday partially buried in the seabed 30 metres (100 feet) underwater.
But no pings were initially detected.
Search officials have since Wednesday focused their efforts on and around the tail, believing the black boxes should be there unless they were dislodged.
Dozens of elite Indonesian Marine divers have tried but failed to thoroughly search the tail because of the powerful currents and the fact it is partially buried in the seabed.
Supriyadi and other Indonesian authorities said divers would continue searching underwater on Friday to track the pings to the black boxes.
He said Indonesian authorities were also planning to try and lift the tail using a crane and floatation devices.
American, Russian and other foreign naval ships were also involved in the hunt for other parts of the plane's wreckage, as well as bodies of most of the passengers.
Just 46 bodies have been found so far, according to Supriyadi.
All but seven of those on board were Indonesian.
The non-Indonesians were three South Koreans, one Singaporean, one Malaysian, one Briton and a Frenchman - co-pilot Remi Plesel.
Supriyadi said another object was found on Friday that could be the nose of the plane, however searchers had yet to reach it to confirm.
"The shape of the object looked like the nose of a plane... we have deployed an ROV (remotely operated vehicle) but the visibility wasn't very good, we are trying to send divers."
Meanwhile, the transport ministry was expected to announce on Friday the findings of an audit into scheduling of flights in the domestic aviation industry.
The ministry launched the probe after alleging that Indonesia AirAsia did not have a permit to fly the Surabaya-Singapore route on a Sunday, the day of the crash.
It also banned Indonesia AirAsia from flying the route, while sacking one transport ministry official and taking disciplinary action against several others for allowing the flight on the Sunday.
Still, investigators have not linked flying on an unauthorised day to the crash.
The Indonesian meteorological agency has said weather was the "triggering factor" of the crash, with ice likely damaging the engines of the Airbus A320-200.
Before take-off, the plane's pilot, Captain Iriyanto, had asked for permission to fly at a higher altitude to avoid a major storm. But the request was not approved due to other planes above him on the popular route, according to AirNav, Indonesia's air traffic control.
In his last communication, the experienced former air force pilot said he wanted to change course to avoid the storm. Then all contact was lost, about 40 minutes after take-off.