A day after the tail of the crashed AirAsia plane was fished out of the Java Sea, the search for the black boxes intensified Sunday, with more pings heard in two different locations amid a growing belief they will soon be recovered.

Three Indonesian ships detected the signals, said Indroyono Soesilo, coordinating minister for Maritime Affairs. They were located about 3.5 kilometres from where the aircraft's rear was discovered.

"The two are close to each other, just about 20 metres," Soesilo told reporters. "Hopefully, they are the cockpit voice recorder and flight data recorder."

However, Tonny Budiono, team coordinator at the Directorate of Sea Transportation, said in a statement that the signals were intense in one area, and that he believed the recorders were likely lodged there beneath wreckage. If divers are unable to free it, all of the debris will be lifted, the statement said.

Other officials cautioned it was too soon to know whether the sounds were coming from the black boxes, which detached from the tail when the plane plummeted into the sea Dec. 28, killing all 162 people on board.

"Until now, I have not yet received reports that the black boxes have been discovered," said Henry Bambang Soelistyo, chief of Indonesia's search and rescue agency. "There are signals, or pings, which are suspected to be of the black boxes."

The Commission for Transportation Safety stopped a remote-operated vehicle from being deployed to probe the area where the pings were heard, fearing it could potentially cause damage to the boxes, said Muhammad Ilyas, head of oceanic surveys at Indonesia's technology agency. Instead, the sites will be examined by divers.

In addition, sonar on Sunday detected a large object in the same vicinity as the pings. Officials initially were hopeful it was the main section of the Airbus A320's cabin, but Soelistyo said divers had confirmed it was instead a wing and debris from the engine.

Search efforts have been consistently hampered by big waves and powerful currents created by the region's rainy season. Silt and sand, along with murky river runoff, have created blinding conditions for divers.

The tail's excavation was a major success in the slow-moving hunt for victims and wreckage from Flight 8501. The red metal chunk from the tail, with the words "AirAsia" clearly visible across it, was brought to the surface on Saturday using inflatable balloons.

Still searching for main fuselage

But the find was tinged with disappointment when the black boxes were not found still attached. Their beacons emit signals for about 30 days until the batteries die, meaning divers have about two weeks left before they go silent.

The debris from the tail was brought up from a depth of about 30 metres and towed to a ship, where it was hoisted onto the deck. The vertical stabilizer was still largely intact, but the attached jagged fuselage was ripped open and tangled by a mess of wires.

INDONESIA-AIRPLANE/

The tail of AirAsia QZ8501 passenger plane is seen on the deck of the Indonesian Search and Rescue (BASARNAS) ship Crest Onyx after it was lifted from the sea bed, south of Central Kalimantan on Saturday. (Prasetyo Utomo/Reuters)

AirAsia CEO Tony Fernandes expressed optimism earlier Sunday that the effort was gaining momentum.

"Let's hope today is a major breakthrough day and we can find [the] main fuselage," he wrote in a Twitter post.

Many believe most of the victims' bodies are likely entombed inside the aircraft on the seabed. So far, only 48 corpses have been recovered.

Several other large objects have been spotted in the search area by sonar, but they have not yet been explored underwater.

Three more bodies were identified Sunday, including Park Seongbeom, 37, and his wife, Lee Kyung Hwa, 34, from South Korea, said Budiyono, who heads East Java's Disaster Victim Identification unit and, like many Indonesians, uses only one name.

He said they were discovered Friday on the seabed, still strapped to their seats. Their baby has not yet been found, but the infant's carrier was still attached to the man.

Sixteen recovered corpses remain unidentified, partially due to decomposition, Budiyono said. Nearly all of the passengers were Indonesian.

The last contact the pilots had with air traffic control, about halfway into their two-hour journey from Indonesia's second-largest city, Surabaya, to Singapore, indicated they were entering stormy weather. They asked to climb from 9,753 metres to 11,582 metres to avoid threatening clouds, but were denied permission because of heavy air traffic. Four minutes later, the plane dropped off the radar. No distress signal was issued.