PARIS (AP) — 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 U.S. 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 remains. Local media report that it may take six months to identify the victims' remains, although death certificates should be issued in two weeks. The 157 who died in Sunday's crash came from 35 countries.