Divers have retrieved one of the black boxes and located the cockpit voice recorder from the AirAsia plane that plummeted into the Java Sea in December, killing all 162 people aboard.

The retrieval is a major breakthrough in the slow-moving hunt to understanding what brought down Flight 8501 on December 28.

On Monday, divers also located the cockpit voice recorder from the flight but have not yet been able to free it from debris on the floor of the Java Sea.

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The flight data recorder was found under part of the plane’s wing and brought to the surface early in the morning, said Henry Bambang Soelistyo, head of the national search and rescue agency.

Divers began zeroing in on the site a day earlier after three Indonesian ships picked up intense pings from the area.

But they were unable to see it due to strong currents and poor visibility, said Suryadi Bambang Supriyadi, operation coordinator at the national search and rescue agency.

He earlier said the black box was lodged in debris at a depth of about 30 metres. He did not provide additional details on the discovery.

Searchers will continue scouring the seabed to try to locate the other black box.

The flight data recorder will be taken to Jakarta for analysis. It could take up to two weeks to download its recorded data, said Nurcahyo Utomo, an investigator at the National Committee for Safety Transportation.

Officials recovered the aircraft’s tail on Saturday, the first major wreckage excavated from the crash site.

They were hopeful the black boxes were still inside, but learned they had detached when the plane crashed into the sea.

Search efforts have been hampered consistently by big waves and powerful currents created by the region’s rainy season.

Silt and sand, along with river runoff, have created blinding conditions for divers.

So far, only 48 bodies have been recovered. Many believe most of the corpses are likely still inside the main cabin, which has yet to be located.