The probe into this month’s Boeing Co. 737 Max crash is turning to the jet’s black-box data as an international investigation team gathers in Ethiopia.

After downloading the March 10 flight’s data and cockpit audio, France’s civil aviation safety authority is sending three investigators to help the Ethiopian probe. All analysis will be carried out by Ethiopians at their investigating bureau, a spokesman for France’s Bureau d’Enquetes et d’Analyses said late Wednesday.

With pressure mounting on Boeing and the troubled jet’s certification process, finding the cause of the disaster has become critical. Airlines and aviation regulators around the world have grounded Max fleets, leaving the immediate future of Boeing’s best-selling aircraft hanging in the balance. The latest crash was the model’s second in less than five months.

While Ethiopia is leading the investigation, other agencies including the BEA, the U.S. Federal Aviation Authority, the U.S. National Transportation Safety Board, as well as Boeing, have been invited to take part, the BEA spokesman said.

Ethiopian Airlines Flight 302 crashed shortly after takeoff from Addis Ababa, killing 157 people. In October, another 737 Max operated by Indonesia’s Lion Air plunged into the Java Sea with 189 aboard. Attention has focused on the model’s anti-stall system, and Ethiopian, U.S. and Canadian authorities concluded there are clear similarities between the two incidents.

The pilot of Flight 302 hadn’t received training on a 737 Max 8 simulator, even though the carrier installed it in January, the New York Times reported. Boeing has said that experienced 737 pilots needed little training for the new aircraft, the newspaper said.

In the case of the doomed Lion Air jet, the same aircraft was saved from disaster the previous day only when an off-duty pilot told the crew how to disable a malfunctioning flight-control system.

Meanwhile, the U.S. Transportation Department has ordered a full audit of the Max’s 2017 certification. The Justice Department is also using a grand jury to help gather information. For months, investigators representing the two departments and the Federal Bureau of Investigation have been digging into a range of matters related to the stall-prevention, called the Maneuvering Characteristics Augmentation System, or MCAS, that pilots were battling throughout the doomed Lion Air flight, Bloomberg reported.

Read: U.S. Said to Have Probed Boeing 737 Max, Pilot Manuals Last Year

Boeing has said it will soon release a software update and pilot training for the 737 Max that will address concerns stemming from the Lion Air accident.

The voice and data recordings from Flight 302 were initially sent to France after Ethiopia refused to hand them to the U.S. Officials in Boeing’s home country had kept the model flying after most other regulators had grounded it.

Ethiopian Airlines had said the initial decision to send the black boxes to Europe was strategic after the FAA was left isolated in the days after the crash, arguing that the Max should continue flying.

The NTSB, the FAA and Boeing took part in the technical work done at the BEA. The French agency has handled other fatal air-disaster investigations in the past including for Air France Flight 447, which was lost in the Atlantic Ocean in 2009, and Germanwings Flight 9525, which was flown into the mountain in 2015 by its co-pilot.