Indonesian divers on Tuesday retrieved the cockpit voice recorder from beneath the wreckage of an AirAsia plane that crashed into the Java Sea as the airline's boss vowed to overcome the "toughest times" he has known.

It came a day after the plane's other black box, the flight data recorder, was recovered, and the devices should provide investigators with vital information about what caused the accident.

Flight QZ8501 went down on December 28 in stormy weather as it flew from the Indonesian city of Surabaya to Singapore with 162 people on board.

Just 48 bodies have so far been recovered, with many believed to be in the main section of fuselage, which has not yet been found.

Indonesia's meteorological agency has said that the bad weather likely caused the Airbus A320-200 to crash but a definitive answer is impossible without the data recorders.

Rescuers faced a lengthy, difficult search often hampered by bad weather but a key breakthrough came at the weekend when they finally detected "ping" signals from the black boxes.

On Tuesday an official involved with the search, who requested anonymity, confirmed that the cockpit voice recorder "has been found and lifted from the sea". The official added that the device had been taken to the navy ship Banda Aceh.

The flight data recorder monitors information such as airspeed, while the cockpit voice recorder stores radio transmissions and sounds in the cockpit. Both are located near the rear of the plane and designed to survive underwater.

The accident is the first major setback for Malaysia-based AirAsia, which has enjoyed a 13-year run of success.

But its flamboyant boss Tony Fernandes pledged Tuesday that the airline would overcome the crisis.

"Rest assured, we are committed to reviewing and improving our products and services. We are more focused than ever to provide you with nothing but the best," he said in a message.

"Even in our toughest times, we will continue to be the world's best and be better for you."

Lengthy analysis

Officials have said they believe the flight data recorder is in good condition and it has already been flown to Jakarta.

Indonesia's National Transport Safety Committee said the boxes would undergo a lengthy analysis in the capital, with the help of a team of experts including from France and manufacturer Airbus.

The committee has said a preliminary report on the accident will be produced within a month, and a final report after a year.

Officials on Monday revealed dramatic new details of the accident, saying a rapid change in pressure caused the plane to "explode" as it hit the water.

"It exploded because of the pressure," said S.B Supriyadi, a director from the search and rescue agency.

"The cabin was pressurised and before the pressure of the cabin could be adjusted, it went down -- boom. That explosion was heard in the area."

The search has involved US, Chinese and other international naval ships.

The tail of the plane, with its red AirAsia logo, was lifted out of the water on Saturday using giant balloons and a crane. It was brought by tugboat on Sunday to a port near Pangkalan Bun on Borneo, the search headquarters.

All but seven of those on board the flight were Indonesian.

The bodies of a South Korean couple were identified on Sunday, but their 11-month-old baby remains unaccounted for.

The other foreigners were one Singaporean, one Malaysian, one Briton and a Frenchman -- co-pilot Remi Plesel. Their bodies have not been recovered.

While the cause of the crash is unknown, the disaster has once again placed Indonesia's chaotic aviation industry under scrutiny.