Investigators examining black box recordings from the doomed Ethiopian Airlines flight have found "clear similarities" with a previous crash.
Last week's crash of a Boeing 737 Max was the second disaster involving the aircraft type in five months.
The French BEA accident authority did not detail the similarities, but media reports suggested they found similar flight angles before the crashes.
It comes amid continuing questions over 737 Max's design and vetting to fly.
Regulators across the world have grounded the aircraft until further notice.
Boeing: What next after the 737 Max disasters? Empty coffins buried after Boeing 737 Max 8 crash Boeing to upgrade software on Ethiopian Airlines crash jet
In a short statement on Monday, the Paris-based BEA, whose experts have been asked by Ethiopian Airlines to examine the black boxes, said: "During the verification process of the FDR (flight data recorder) data, clear similarities were noted by the investigation team between Ethiopian Airlines Flight 302 and Lion Air Flight 610, which will be the subject of further study during the investigation."
Both the Ethiopian Airlines flight eight days ago and a Lion Air aircraft in October crashed within minutes of take-off.
In the case of the Lion Air flight, pilots had difficulties with a new system on the Boeing 737 Max which is designed to keep the plane from stalling.
Questions
It prevents a jet from pointing upwards at too high an angle, where it could lose its lift.
But an investigation of the Lion Air flight showed the automatic anti-stalling system repeatedly forced the plane's nose down more than 20 times.
Ethiopia's Transport Ministry and the US Federal Aviation Administration (FAA) have both pointed to similarities between the two disasters.
US regulators and safety experts are now asking how thoroughly the FAA and Boeing vetted the anti-stall system and how well pilots around the world were trained for it when their airlines bought new planes.
Over the weekend, a report in The Seattle Times claimed that some analysis before the crash found that the system, called the Maneuvering Characteristics Augmentation System, revealed crucial flaws.
It claims that managers at the FAA instructed its safety engineers to delegate safety assessments to Boeing and to approve the resulting analysis.
The report alleges that the analysis produced by Boeing understated the power of the control system and that it could reset itself every time the pilot responded.
This meant that the system could repeatedly push the nose of the plane down.
The FAA said its "aircraft certification processes are well established and have consistently produced safe aircraft designs."
"The 737-MAX certification program followed the FAA's standard certification process," it added.
Boeing has been contacted for comment.
The world's biggest planemaker says the 737 Max is safe, but after the Lion Air crash last year, it began plans to roll out a new software upgrade.