The flight from Kuala Lumpur to Beijing went missing in March 2014, with 239 passengers and crew on board. Despite extensive searches at a cost of nearly NZ$152 million, the main body of the airplane was never located.
Malaysia's government released its findings on July 30 in a 400-page report. The findings concluded the plane's diversion from its planned route was likely made "under manual control" - and couldn't "exclude the intervention of a third party".
However the report said the lack of evidence meant they still don't know why the plane disappeared.
But the report has been slammed by victims' families who say it's covering up what really happened to the plane.
Voice 370, a group of the victims' relatives, is accusing the Malaysia government of withholding flight data and failing to consider all options - including a murder-suicide by the chief pilot.
French authorities are also unsatisfied with the findings, and now the Gendarmerie of Air Transport (GTA) has launched its own probe.
It intends to examine data from the satellite operator which tracked the plane to "verify the veracity and especially the authenticity of all the technical data transmitted", according to French newspaper Le Parisien.
Voice 370 said it supports the French decision in a statement issued earlier this week.
"The French authority mentions repeatedly in their report that their investigations on the flaperon had been hampered by an absence of data from Boeing," it says.
"The report highlights that the military's primary radar data played a significant role in tracing the aircraft's flight path. Voice 370 calls upon the Government of Malaysia to share all available data with independent experts for a thorough peer review and analysis.
"We believe that after 4.5 years since MH370 disappeared, there is no reason to continue to withhold data when its probative value far outweighs any prejudicial effect."