Investigators in Indonesia have ruled out terrorism as a cause for the Air Asia crash in the Java Sea last month.

They've been examining the jet's black box data recorders - saying the pilot seems to have been 'busy with the handling of the plane' in the 'critical situation'.

A team of navy divers retrieved the flight data recorder from the AirAsia plane which crashed in the Java Sea last week. Salvage experts earlier discovered the black box beneath debris from the main section of the plane, but were unable to recover it.

AirAsia flight 8501 came down on route from Surabaya in Indonesia to Singapore a fortnight ago with 162 people on board.

On Saturday, a section of the plane's tail section was pulled from the sea, raising hopes that the black box would be found soon. Electronic signals, called pings, had also been heard.

There are normally two in-flight data recorders - one that holds flight data and one that records the voices of those in the cockpit. Both are usually housed in the tail of an Airbus A320-200.

More pings have reportedly been heard in two different locations in the preceding 24 hours since the tail fin was removed from the water.

Indroyono Soesilo, coordinating minister for maritime affairs, said they were located around two miles from where the aircraft's tail was discovered.

"The two are close to each other, just about 20 metres," Mr Soesilo told reporters. "Hopefully, they are the cockpit voice recorder and flight data recorder."