A woman stand in front of an AirAsia check-in machine at Soekarno Hatta airport in Jakarta, January 21, 2015. [Photo/Agencies]

JAKARTA - Indonesian National Transportation Safety Committee or KNKT will soon announce the preliminary result of probe on the crashed AirAsia plane last month that killed all 162 people on board, investigator disclosed here on Thursday.

The preliminary result of the investigation would report the content of both Cockpit Voice Recorder (CVR) and Flight Data Recorder (FDR), including the report at the moment shortly before the crash, KNKT investigator Sulaiman told Xinhua via phone.

"The content of the report is about what was recorded by the CVR. It is about the situation at seconds before the crash. It is still raw materials," said the official.

The AirAsia flight QZ8501 crashed on December 28 in waters off Central Kalimantan of Indonesia when it was flying from Surabaya of Indonesia enroute for Singapore.

Both flight data recorder and voice cockpit recorder have been delivered to the KNKT.

The jet was in sound condition and all crew members were properly certified, Indonesia's National Transportation Safety Committee said on Thursday.

Mardjono Siswosuwarno, head investigator for the National Transportation Safety Committee, told reporters the flight data recorder provided a "pretty clear picture" of what happened in the last moments of AirAsia Flight QZ8501.

He added that the first officer was flying the plane at the time of the accident.