Pangkalan Bun: Signals believed to be from the black box data recorders of crashed AirAsia Flight 8501 were detected Friday, Indonesian authorities said, offering the strongest lead to explain the disaster.

However more of the bad weather that has plagued the 13-day search for the doomed plane stopped divers from quickly tracking the ping signals to the black boxes, and frustrated efforts to lift the plane’s tail from the floor of the Java Sea.

“A ship detected the pings. The divers are trying to reach it,” said S.B Supriyadi, a director with the National Search and Agency who is stationed at search headquarters in the town of Pangkalan Bun on Borneo island.

“The location of the ping is reported to be near where the tail was found.”

The plane crashed on Dec. 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, which is lying 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 meters 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, in a task complicated by powerful currents and the fact it is partially buried in the seabed.

Those problems continued throughout Friday, with efforts to lift the tail using floatation devices scuppered by rough seas.

“We have tried (to lift the tail) but it was unsuccessful. We are still trying,” Supriyadi told AFP.