"We found one of the black boxes," Soerjanto Tjahjono told AFP, adding that it was not clear whether it was the flight data recorder or cockpit voice recorder.

The Boeing-737 MAX 8, which went into service just a few months ago, plunged into the Java Sea off Indonesia's northern coast on Monday, killing 189 people, just 12 minutes after taking off from the capital Jakarta for Pangkal Pinang city.

The single-aisle Boeing plane is one of the world's newest and most advanced commercial passenger jets.

"Data from the plane -- the engine, all the instruments -- are recorded there," said aviation analyst Dudi Sudibyo told AFP.

"If there is an anomaly, some technical problem, it is recorded there too."

Images from the crash site showed two divers swim to a support vessel and place an orange-coloured device into a plastic tub, which was then carried onto the boat.

Despite the name, the two black boxes are in fact bright orange with reflective stripes, and all commercial planes are obliged to have them on board.

Authorities picked up the box's signals below the water's surface on Wednesday, but were unable to get to the device immediately because of rough seas and strong currents.

The treasure trove of information black boxes provide helps explain nearly 90 percent of all crashes, according to aviation experts.

They each weigh seven to 10 kilograms (15 to 22 pounds) and can survive as deep as 6,000 metres (almost 20,000 feet) underwater or an hour at 1,100 degrees Celsius (2,012 degrees Fahrenheit). To make them easier to find, they are fitted with a beacon which can emit a signal for one month.

DNA testing

Dozens of divers are taking part in the massive recovery effort along with helicopters and ships, but authorities have all but ruled out finding any survivors.

On a Jakarta dockside, grief-stricken relatives sifted through clothes, wallets and other retrieved personal effects, as authorities sent body parts to hospital for DNA testing.

Forensic experts identified Jannatun Cintya Dewi as the first victim of the crash Wednesday evening.

The 24-year-old's coffin arrived in her East Java hometown Sidoarjo Thursday, draped in a green and yellow cloth and inscribed with Arabic writing and carried through the neighbourhood by pallbearers.

Dewi's mother collapsed and had to be carried into their home, while friends and relatives wiped away tears as the casket was laid in a freshly dug grave sprinkled with flowers, a bowl of fruit and two palm branches at one end.

Aviation experts say it is too early to determine what caused the accident.

But Lion's admission that the aircraft had an unspecified technical issue on a previous flight -- as well as the plane's abrupt nosedive -- have raised questions about whether it had any faults specific to the newly released model, including a speed-and-altitude system malfunction.

The accident has also resurrected concerns about Indonesia's patchy air safety record which until recently saw the country's carriers facing years-long bans from entering European Union and US airspace over their safety records.

Lion Air has been plagued by safety woes and customer complaints over unreliable scheduling and poor service.

The budget carrier was involved in a number of incidents including a fatal 2004 crash and a collision between two Lion Air planes at Jakarta's Soekarno-Hatta airport.