Personnel from Indonesia's national disaster agency transfer a body bag containing the recovered remains of a passenger from AirAsia flight QZ8501 at the port of Kumai. -AFP

AFP/ Jakarta

Investigators examining the cockpit voice recorder of a crashed AirAsia jet said on Tuesday they were considering whether human error or problems with the plane caused the accident, after ruling out terrorism.

Flight QZ8501 went down in the Java Sea on December 28 in stormy weather with 162 people on board, during what was supposed to be a short trip from the Indonesian city of Surabaya to Singapore.

Indonesian divers have recovered the Airbus A320-200's black boxes, the cockpit voice recorder and the flight data recorder, and so far have found 53 bodies.

The plane's main body -- believed to contain the bulk of the victims -- was spotted by a navy ship last week, but attempts to reach it in recent days have failed due to bad weather and rough seas.

Indonesia's National Transportation Safety Committee (NTSC), which is probing the crash, said that it will release a preliminary report on January 28.

In initial analysis of the cockpit voice recorder, NTSC investigators said they did found no indication that terrorism had caused the crash and are now looking at other causes.

"We didn't hear any other person, no explosion," investigator Nurcahyo Utomo told reporters, explaining why terrorism had been ruled out.

He added that investigators were now looking at the "possibility of plane damage and human factors," without giving further details.

Indonesia's meteorological agency has said bad weather may have caused the crash. Utomo said investigators would focus on how the systems in place and people responded to the weather, rather than just the conditions themselves.

Investigators are also examining a wealth of information in the flight data recorder, which monitors every major part of the plane and records its altitude and the direction it was flying in.

Another investigator, Ertata Lananggalih, said authorities would not disclose any further details about the contents of the recorders before the release of the preliminary report. 

There was a huge international hunt for the crashed plane, involving ships from several countries including the US and China. All but seven of those on board the flight were Indonesian.