Indonesian divers on Sunday located the flight recorders of the AirAsia plane that crashed into the Java Sea, but were unable to retrieve them because they were wedged between two pieces of the aircraft, the Transport Ministry said.

Searchers will try to lift the aircraft's part using underwater lifting bags and retrieve the recorders, known as the black boxes, on Monday, the ministry said in a statement on its website.

Air Commodore Suryadi Supriyadi, the search operation chief, said earlier that sonar equipment also detected a large object around the same location as the flight recorders.

"We suspect it's the aircraft's main body," he said on the local broadcaster Metro TV.

Officials believe that many of the victims are still trapped in the aircraft's fuselage.

Searchers lifted the aircraft's tail from the bottom of the sea on Saturday but did not find the recorders.

Data from the recorders help investigators determine the chain of events leading to an accident, and the root cause of it.

Officials said the recorders, which are normally located in a passenger jet's tail, could have been detached from the plane as it crashed.

The search to find the black boxes is a race against time as the devices' batteries are designed to transmit signals for up to 30 days. The plane crashed on Dec 28.

The homing beacon emitted by one of the recorders appeared to be about a kilometre from where the tail section was found, based on the signal detected by Indonesian ship KN Jadayat.

AirAsia flight QZ8501 was flying from Surabaya to Singapore when it disappeared from radar somewhere above the Karimata Strait in the Java Sea.

So far, 48 bodies have been retrieved from the water, but no survivors have been found.

Two of three bodies identified Sunday were those of a South Korean couple - Seong Beom Park and Kyung Hwa Lee - who were among the passengers, said Budiyono, the head of the East Java police disaster victim identification department.

Most of the passengers were Indonesians.

- dpa