How the doomed AirAsia flight QZ8501 crashed into the Java Sea two weeks ago, killing all 162 people on board, won’t be known until a report is completed within one month and a final report after one year, investigators say.

Divers recovered the black box voice recorder on Tuesday which will now be sent to Jakarta for analysis.

The second black box was found not far from where the flight data recorder was recovered on Sunday.

• AirAsia flight QZ8501 ‘experienced explosion’
• Divers struggle to reach AirAsia wreckage

The plane was less than halfway into a flight from Surabaya, Indonesia, to Singapore on December 28, when it lost contact with air traffic control in stormy weather.

Bad weather has hampered efforts by recovery crews to salvage wreckage from the flight.

National Transportation Safety Committee investigator Santoso Sayogo told the AFP news agency that the voice recorder was taken on board an Indonesian navy vessel and was expected to be sent to Jakarta for analysis.

But the claims were not officially confirmed by the NTSC or the National Search and Rescue Agency BASARNAS.

The head of the transport safety committee Tatang Kurniadi said the flight data recorder looked to be in good condition.

But investigators may need up to a month to get a complete reading of the data.

“The download is easy, probably one day,” NTSC head investigator Mardjono Siswosuwarno says.

“But the reading is more difficult … could take two weeks to one month.”

The committee said a preliminary report on the incident would be produced within a month and a final report after a year.

Forty-eight bodies have been retrieved from the Java Sea and brought to Surabaya for identification.

Searchers believe more bodies will be found in the plane’s fuselage.

Relatives of the victims have urged authorities to make finding the remains of their loved ones the priority.

The news comes after AirAsia CEO Tony Fernandes sent an email to customers saying the airline would emerge from the tragedy stronger.

“The past few weeks have been the most difficult weeks of my life since starting AirAsia 13 years ago,” Fernandes, 50, said in an email to customers on Tuesday.

“I wanted to reach out and thank you for the warmth and support given to all of us. Your messages of love and encouragement strengthen our resolve to be better.”

– with AAP