Investigators have completed the initial data extraction from the voice recorder of the ill-fated Jeju Air passenger plane's black box.

The Ministry of Land, Infrastructure and Transport said in a briefing on Wednesday that investigators proceeded with the initial data extraction from the voice recorder, which was recovered relatively intact.

The black box is divided into a voice recorder and a flight data recorder.

Currently, efforts are underway to convert the data into voice form.

However, the flight data recorder, which logs the aircraft's altitude, direction, time and other information, is missing a key connector necessary for analysis, leading to its slow progress.

The ministry said in a separate briefing later in the day that it has agreed with the U.S. National Transportation Safety Board(NTSB) to transport the flight data recorder to the U.S. to extract and analyze the information.