The plane, carrying 189 people, crashed soon after taking off from Jakarta, the Indonesian capital, on Monday.

It plummeted into the Java Sea - no survivors have been found, nor has the body of the Boeing 737.

There is as yet no indication of what caused the crash, but the aircraft is believed to have experienced technical problems on its penultimate flight.

The plane was making a one-hour journey to the western city of Pangkal Pinang when it went down.

The pilot had asked air traffic control for permission to turn back to the airport, but then contact was lost.

Buried on the sea floor

A diver told reporters on board one of the search and rescue vessels scouring the Java Sea: "We dug and we got the black box."

The diver, identified as Hendra, said the box had been buried in debris on the sea floor, Reuters reports.

Officials say it was a data recorder, and that they are still searching for a second "black box" which would have recorded conversations between the two pilots.

Local news channel Metro TV showed footage of the box, inside a plastic crate, being brought onto a ship.

Recovering the flight recorder means aviation safety experts can begin piecing together the plane's final moments to work out what went wrong. But it could take up to six months to analyse data from the black boxes, officials from Indonesia's transportation safety committee have said.

A log obtained by the BBC showed the plane had experienced technical problems while flying from Bali to Jakarta the previous day.

The log showed one instrument was giving "unreliable" airspeed readings and the captain had to hand over to the first officer. Altitude readings also differed on the captain and first officer's instruments.

Lion Air, a budget airline based in Indonesia, has acknowledged a technical problem occurred on the penultimate flight but said it was resolved "according to procedure".

The company has sacked its technical director, Muhammad Asif. Representatives from Boeing are also meeting Indonesian officials as part of the investigation.

Meanwhile, search officials are continuing the grim task of gathering body parts found at the crash site and taking them to land for identification.

On Wednesday night, the funeral was held of the first identified victim, a 24-year-old woman who worked in the engineering ministry.