Indonesian authorities have said they have detected pings during the black box search of the crashed AirAsia flight QZ8501.

This is the first time such pings have been recorded in 12 days, after the plane with 162 people on board went off radar and crashed in the Java sea.

"We received an update from the field that the pinger locator already detected pings. We have our fingers crossed it is the black box. Divers need to confirm. Unfortunately it seems it's off from the tail. But the divers need to confirm the position," Santoso Sayogo, an investigator at Indonesia's National Transportation Safety Committee said.

The flight data recorders sends beacon signals up to 30 days if a plane crashes, in order to help locate the aircraft's black boxes.

As the flight's recorders contain crucial data leading up to the crash, it would throw light on the cause of the tragedy.

The AirAsia flight went off radar on 28 December and so far no survivors have been found.

"For today's operations, we will use helicopters to carry the balloons that will assist in lifting the tail," Lieutenant Colonel Penerbang Jhonson Hendrico Simatupang told Reuters.

"But we are expecting sudden changes later in the day. So we're taking advantage now and moving the balloons as fast as we can."

So far, 48 dead bodies have been recovered from the Java sea.