Data retrieved from the crashed EgyptAir flight recorders has confirmed reports suggesting that the plane caught on fire before disappearing from radars and plunging into the Mediterranean, killing 66 passengers in May, investigators said.

“Recorded data is showing consistency with ACARS [Aircraft Communications Addressing and Reporting System] messages of lavatory and avionics smoke,” the aircraft investigation committee reported after it embarked on examining the contents of one of two black boxes retrieved from the Mediterranean.

The heat damage incurred to the debris and the signs of soot on the wreckage is another evidence in support of the fire on board version, the committee added.

In May, France’s Bureau of Enquiry and Analysis [BEA] for civil aviation safety confirmed the ACARS had sent a series of messengers indicating smoke in the lavatory and avionics bay.

The experts hope the black box’s data will shed the light on the sequence of events preceding the crash as it appears to record the flight in full.

“Preliminary information shows that the entire flight is recorded on the FDR since its takeoff from Charles de Gaulle Airport until the recording stopped at an altitude of 37,000 feet where the accident occurred,” the committee said.

The cockpit voice recorder, is still waiting to be read, as the BEA is working to restore the device in its laboratory in France. Both black boxes were severely damaged as they were retrieved from the seabed at a depth of 13,000 feet (4,000 meters) on June 16 and June 17 by the search boat John Lethbridge, just a week before they were supposed to cease sending signals.

Details of the cabin crew’s conversation are expected to resolve the mystery surrounding the causes of the A320 airliner tragedy, with the evidence increasingly suggesting the plane was brought down by some kind of a technical failure.

On Monday, the Paris prosecutor’s office initiated a probe into the deadly crash, citing charges of “involuntary homicide,” adding the version of terrorist conspiracy is not regarded viable by the prosecution and would not be considered.

Prior to the black boxes’ discovery, the flight experts came up with a vast specter of different versions of what could have brought the plane down, ranging from hijacking or sabotage to the explosion on board.

The latter version, however, was dismissed by Egyptian forensics authority as unsubstantiated on May 24. The proponents of the hypothesis argued that the manner in which the human remains were scattered might indicate that the explosion could have led to the catastrophe.

The EgyptAir flight MS804 was heading from Charles de Gaulle Airport in Paris to Cairo as it disappeared from the radar close to the Egyptian coast on May 19 and crashed into the Mediterranean. The first debris of the plane were subsequently spotted 290 kilometers north of the city of Alexandria, Egypt. Fifty-six passengers, the majority of them Egyptian and French nationals, and 10 crewmembers were all killed in the crash.