PANGKALAN BUN, Indonesia/JAKARTA (Reuters) - Indonesian search and rescue teams hunting for the wreck of an AirAsia passenger jet detected pings they believed were from the plane's black box flight recorders on Friday, 12 days after it went missing with 162 people on board.
Indonesia AirAsia Flight QZ8501 vanished from radar screens on Dec. 28, less than half way into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore. There were no survivors.
Forty-eight bodies, including at least two still strapped to their seats, have been found in waters off Borneo, but strong winds and high waves have hampered efforts to reach larger pieces of suspected wreckage detected by sonar on the sea floor.
The Airbus A320-200 carries the cockpit voice and flight data recorders, key to the investigation into why the airliner crashed, near the tail of the plane.
However, officials said it looked increasingly likely that they had become separated during the disaster.
"We detected signals about 1 km away from the location of the tail," search and rescue agency coordinator Supriyadi told reporters in Pangkalan Bun, the southern Borneo town closest to the crash site.
"Reports from the field confirm that pings are from the black box, because once the search team were out of a 500 m range, they could no longer hear it," he added.
"Tomorrow we will continue searching by air. We will add ships to the search. We will deploy divers to investigate more objects that have been detected but not yet identified."
The search operation so far appears to have relied heavily on sonar imagery and divers to locate the black boxes, but industry experts have questioned whether acoustic equipment, especially designed to pick up signals from underwater locator beacons, should have been employed more in the initial phase.
If and when the recorders are located and taken to Jakarta for analysis, it could take up to two weeks to download data, investigators said, although the information could be accessed in as little as two days if the devices are not badly damaged.
While the cause of the crash is not known, the national weather bureau has said seasonal tropical storms common in the area were likely to be a factor.
Poor weather and visibility thwarted hopes on Friday of using balloons to lift the tail section from the seabed.
"We haven't been able to get inside the tail yet," said Rudi Hartanto, a navy diver and underwater video team leader who dove twice in the morning and filmed frogmen attaching balloons.
"At the most we can just fit our heads in, but can't see anything because the visibility is low. We haven't seen any black box ... We are not sure if the black box is there."
The tail was found on Wednesday, upturned on the sea bed about 30 km (20 miles) from the plane's last known location at a depth of around 30 meters.
The head of the search and rescue agency, Fransiskus Bambang Soelistyo, told reporters that two bodies had been found still attached to their seats, with local television reporting that one of the recovered seats was from the cockpit.
"Looking for victims is still our main priority besides the black box," he said.
Relatives of the victims have urged authorities to make finding the remains of their loved ones the priority.
Indonesia AirAsia, 49 percent owned by the Malaysia-based AirAsia budget group, has come under pressure from the authorities in Jakarta since the crash.
The transport ministry has suspended the carrier's Surabaya-Singapore license, saying it only had permission to fly the route on Mondays, Tuesdays, Thursdays and Saturdays.
Flight QZ8501 took off on a Sunday, though the ministry said this had no bearing on the accident.
On Friday, the Transport Ministry announced it had found five other airlines had violated rules by flying some routes without permits, and that they would be prevented from using those routes until they obtained the necessary documentation.
They included state carrier Garuda Indonesia and private airline Lion Air.
Additional reporting by Gayatri Suroyo, Nicholas Owen, Michael Taylor, Eveline Danubrata, Wilda Asmarini and Nilufar Rizki in Jakarta and Fransiska Nangoy in Surabaya; Writing by Nick Macfie; Editing by Mike Collett-White