Black boxes from the crashed EgyptAir Flight 804 will be sent to the French aviation accident investigation bureau, near Paris, for repair after attempts to extract information from the recorders failed, Egyptian investigators said late Thursday. A cockpit voice recorder and second black box of the Airbus A320 were found last week. 

The Cairo-bound Flight 804 crashed into the Mediterranean Sea shortly after entering Egyptian airspace May 10, killing all 66 people on board. Some wreckage of the plane has been recovered and investigators from France and the United States are assisting Egyptian officials to establish the cause of the crash.

The “electronic boards” of the recorders will be sent back to Cairo for analyzing the flight data following the repair, Egypt’s Investigation committee said in a statement. Investigators had earlier said it would take “lots of time and effort” to examine the damaged black boxes.

Black boxes give investigators critical data, including the pilots’ transmissions, information about the working of plane’s engines, navigation systems, and auto-pilot working and smoke alarms. It remains unclear what led to the crash of MS804, but terrorism has not been ruled out.

Luggage and body parts have been found some 180 miles from the Egyptian port city of Alexandria. Investigators said that the plane, which was en route from Paris to Cairo, veered left off course at about 37,000 feet and made a sharp right turn and completed a full circle. Radar data showed that the plane did not suffer a sudden midair explosion. However, electronic messages sent by the plane indicated some smoke alarms went off.

Egyptian officials also confirmed that Flight 804 sent out a distress call while it went down into the Mediterranean. Authorities said they had “received satellite reports indicating receiving an electronic distress call from the plane's emergency locator transmitter.”