(CNN) Investigators trying to piece together what caused EgyptAir Flight 804 to plunge into the Mediterranean Sea now have another clue.

The plane's cockpit voice recorder indicates there was a fire on the aircraft before it crashed -- and an attempt to put it out, a senior source from the airline told CNN on Tuesday.

The revelation adds another detail to a picture that's been slowly emerging since the May 19 crash. But investigators have said it's still too soon to say what happened aboard the flight.

The cockpit voice recorder captures sounds from the flight deck, including crew conversation, alarms and background noise that can help investigators understand what the flight crew was doing.

revealed details about what can be heard in the recording. French investigators were Authorities haven't released a transcript orrevealed details about what can be heard in the recording. French investigators were working to repair the voice recorder's damaged memory chip

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