Investigators have started studying the cockpit voice recorder of the crashed Ethiopian Airlines jet.
The French air accident investigation agency BEA tweeted that technical work on the recorder began Saturday. The BEA also said work resumed on the flight's data recorders.
The recorders, also known as black boxes, were sent to France because the BEA has extensive expertise in analyzing such devices.
Experts from the US National Transportation Safety Board and the plane's manufacturer Boeing are among those involved in the investigation.
In Ethiopia, forensic DNA work has begun on identifying the remains. It may take six months to identify the victims' remains, although death certificates should be issued in two weeks. The 157 who died in the crash came from 35 countries.
A mass memorial service for the dead is planned in Addis Ababa to take place Sunday, one week after the crash.
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Muslim families have already held prayers for the dead and are anxious to have something to bury as soon as possible.
The Ethiopian disaster and a crash last year in Indonesia were both of the Boeing 737 Max 8 planes. The United States and many other countries have grounded the Max 8s as the US-based company faces the challenge of proving the jets are safe to fly amid suspicions that faulty sensors and software contributed to the two crashes that killed 346 people in less than six months.
The US Federal Aviation Administration said regulators had new data from satellite-based tracking that showed the movements of Ethiopian Airlines Flight 302 were similar to those of Lion Air Flight 610, which crashed off Indonesia in October, killing 189 people.
Both planes flew with erratic altitude changes that could indicate the pilots struggled to control the aircraft. Shortly after their takeoffs, both crews tried to return to the airports but crashed.
Boeing said it supports the grounding of its planes as a precautionary step, while reiterating "full confidence" in their safety.
Engineers are making changes to the system designed to prevent an aerodynamic stall if sensors detect that the jet's nose is pointed too high and its speed is too slow.
Investigators looking into the Indonesian crash are examining whether the software automatically pushed the plane's nose down repeatedly, and whether the Lion Air pilots knew how to solve that problem.
Ethiopian Airlines says its pilots received special training on the software.