French investigators had always leaned towards a mechanical fault as the cause of the crash, saying they suspected that a mobile phone or tablet had caught fire.
In December 2016, Egyptian officials announced that "traces of explosives were found" on victims' remains.
The Airbus A320 plunged into the eastern Mediterranean en route from Paris to Cairo on 19 May, killing all 66 passengers on board.
Because of this, it transferred the case to the Egyptian Prosecution Bureau for further investigation.More news: Nebraska groups react to Pruitt's resignation
The crew also mentioned in a cockpit voice recorder the existence of a fire on board.
Officials recovered flight recorders that were analyzed two months after the crash because advanced fix work was needed first, the new report from investigators with France's Bureau of Enquiry and Analysis for Civil Aviation Safety, known as BEA said.
The French investigation agency BEA said Friday that the "most likely hypothesis" is that a fire broke out in the cockpit and "spread rapidly, resulting in loss of control".More news: UK's May names new foreign secretary
Egyptian authorities are carrying out a criminal investigation amid suspicions that explosives were involved. Upon its determination the act was malicious, Egyptian officials handed the investigation over to judicial authorities.
It said it was waiting for Egypt to publish its final report into the crash to understand how the two countries arrived at different conclusions.
The BEA urged Egyptian prosecutors to investigate the possibility it was an accidental fire, to prevent such accidents in the future.
The French investigator said it stood ready to continue their collaboration with its Egyptian counterpart "should the latter restart the safety investigation into this accident".More news: Netflix Debuts "Smart Download" Feature As Boost For Binges
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