Relatives of the victims of the missing EgyptAir flight MS804 hold an absentee funeral prayer in a mosque nearby Cairo airport, Reuters

The voice recorder from the cockpit of EgyptAir MS804 has been found, Egyptian investigators said on 16 June. The development comes nearly one month after the flight from Paris to Cairo crashed, killing all 66 people on board.

The black box was damaged and had to be recovered in several stages, however, the memory unit of the voice recorder is believed to be intact and could provide new clues into the cause of the crash. It will be taken to Alexandria in Egypt to be studied after being recovered by a search vessel with an underwater robot, called the John Lethbridge.

Investigators said in a statement: "The vessel's equipment was able to salvage the part [of the recorder] that contains the memory unit, which is considered the most important part of the recording device."

The aircraft's manufacturer, Airbus, had previously said that finding the black boxes was crucial to understanding what happened when the flight disappeared off the radar. The cockpit voice recorder is said to contain the last two hours of cockpit audio and will allow investigators to hear what the pilot and co-pilot were saying to each other, as well as whether any alarms were going off in the background.

The cockpit audio is only one part of the black box, which also contains a flight data recorder that would reveal 25 hours of flight information should it be found. However, experts told the BBC that signals from the data recorder will expire by 24 June.

The discovery of the voice recorder comes one day after the Egyptian government said that the search vessel had identified several locations of wreckage from the flight. Debris and human remains have also been found in the search for the plane.

Electronic messages from the plane previously revealed that smoke detectors had gone off inside the toilets and the plane's electrics minutes before the flight vanished from the radar. Greek investigators also believe that the plane turned 90 degrees left and then 360 degrees to the right, before dropping sharply and disappearing from the radar.

However, the crew on board do not appear to have sent a distress call. Although a terror attack has not been ruled out, no extremist group has claimed responsibility for the disappeared plane and analysts have said that human or technical error is a possibility as well.