ADDIS ABABA/PARIS (Reuters) – Investigators seeking the cause of the crash of an Ethiopian Airlines plane that killed all 157 people on board have begun studying the cockpit voice recorder, France’s BEA air accident investigation agency said on Saturday.

Downloading the data from the recorder retrieved from wreckage of the Boeing 737 MAX 8 plane was expected to take four to five hours, a spokesman for the agency said.

The BEA also issued a photo showing the recorder intact but dented by the impact of the plane’s crash into a field on Sunday minutes after take-off from Addis Ababa.

The Ethiopian carrier said DNA testing of the remains of the people on board flight 302 may take up to six months, and it offered bereaved families charred earth from the plane crash site to bury. Passengers from more than 30 nations were aboard.

As families wait for the results from the investigation into the cause of the crash, Ethiopian Airlines is planning to hold a service on Sunday in Addis Ababa, at the Kidist Selassie, or Holy Trinity Cathedral, where many of the country’s past rulers are buried beneath its pink stone spires.

“We were told by the company that we will be given a kilo (of earth) each for burial at Selassie Church for a funeral they will organise,” said one family member who asked not to be named.

Papers given to the families at the Skylight Hotel on Saturday said death certificates would be issued within two weeks, and an initial payment made to cover immediate expenses.

The return of remains – most of which are charred and fragmented – would take up to six months, the papers said, but in the meantime earth from the crash site would be given.

Abdulmajid Sheriff, a Kenyan whose Yemeni brother-in-law died, said the family had already held a service.

“We are Muslims we didn’t care about that (earth). We did yesterday our prayers at the mosque and that is all for us.”

Experts say it is too soon to know what caused the crash, but aviation authorities worldwide have grounded Boeing’s 737 MAXs, as concerns over the plane caused the company’s share price to tumble.

Flight data has already indicated some similarities with a crash by the same model of plane during a Lion Air flight in October. All 189 people onboard were killed. Both planes crashed within minutes of take off after pilots reported problems.

France’s air accident investigation agency said on Saturday it was working on the Ethiopian flight’s black boxes in coordination with teams from Boeing as well as U.S. and EU aviation safety authorities.

The grounding of the 737 MAX jets has had no immediate financial impact on airlines using the planes, but it will get painful for the industry the longer they do not fly, companies and analysts said on Friday.

Boeing plans to release upgraded software for the 737 MAX in a week to 10 days, sources familiar with the matter said.

The U.S. planemaker has been working on a software upgrade for an anti-stall system and pilot displays on its fastest-selling jetliner in the wake of the deadly Lion Air crash.