Investigators in the recovery of AirAsia flight 8501 are saying for the first time that the crash was not the result of a terrorist attack.

In an exclusive interview with Reuters, lead investigators say about 50 percent of the information from the black box flight recorders has been decoded.

The voice from the cockpit doesn't show any sign of a threat, the air safety investigator said. It's only the pilot sounding very busy handling the plane.

The search for the remaining bodies is ongoing, but bad weather continues slow the recovery efforts.

Divers have retrieved the bodies of 51 of the 162 people on board who perished.

Although crews have located the plane's fuselage, strong currents have prevented them from lifting it off the sea floor.

The AirAsia flight lost contact with air traffic control in bad weather three weeks ago during a flight from the Indonesian city of Surabaya to Singapore.