The cockpit voice recorder of the Lion Air jet that crashed into the Java Sea in October, killing 189 people, has been found, an Indonesian official has said.

Navy divers used specialised equipment to find the device under eight metres of seabed mud. The Lion Air jet, crashed into waters 30 metres deep.

Ridwan Djamaluddin, a deputy maritime minister, told reporters on Monday the National Transportation Safety Committee had informed the ministry about the discovery.

He said human remains were also discovered at the seabed location in the waters of Tanjung Karawang on Monday morning.

The two-month-old Boeing 737 Max 8 jet operated by the Indonesian budget airline plunged into the sea just minutes after taking off from Jakarta on 29 October, killing all on board.

The CVR, which records conversations between the pilots, co-pilots and air traffic control, is believed to hold vital clues into the fatal crash. Indonesian aviation analyst Gerry Soejatman said the finding was “crucial” because it would allow investigators to understand “what was going on in the heads of the pilots during the flight”.

The pilots of the downed plane had requested to turn back two minutes after taking off for Pangkal Pinang, before losing contact with air traffic control.

It is unclear in what condition the black box was found but analyst Soejatman said there were various methods to recover the CVR data.

Luhut Pandjaitan, the maritime and fisheries minister, told the Jakarta Post he hoped the discovery would bring more clarity to the investigation. “It’s very good progress. I think the information in the box might make things clear,” he said.

The first black box to be recovered, the flight data recorder (FDR), was discovered days after the crash.

A preliminary report by Indonesian authorities released in November showed there had been problems with the jet’s airspeed indicator, with the mechanism malfunctioning on the last four flights.

In the days before the crash, an angle of attack sensor, which indicates whether a plane is going to stall, was also replaced.

While the search for the second black box was resumed on 8 January, Indonesians officials had called off the search for the victims in late November.

At the time, 196 body bags containing body parts had been recovered but only 125 victims had been identified, with the condition of the remains complicating the work of the police forensics team.

Lion Air launched a multi-million dollar search effort in late December to continue the search for the remaining victims and second black box.

The crash – the first of a Boeing 737 Max jet and the worst airline disaster in Indonesia in more than two decades, has also heightened concerns about the safety and maintenance operations of Lion Air – a budget airline that has expanded rapidly across south-east Asia over recent years.