Initial attempts to download information from the flight data and voice recorders of the EgyptAir plane that crashed into the Mediterranean last month have failed, The Associated Press reported Thursday.

Due to the failure, key parts of the recorders are being sent to France for repairs, Egyptian and U.S. officials said.

The “electronic boards” of the recorders are being flown next week to the offices of the French aviation accident investigation bureau near Paris, according to AP. After the boards are repaired and salt removed, they will be sent back to Cairo for data analysis, Egypt’s Investigation committee said in a statement late Thursday.

“Black boxes” are the crucial components of any aircraft which record the plane’s movements and technical settings at any given time in the flight data recorder, as well as audio from the cockpit in the cockpit voice recorder.

Two weeks ago, a French vessel picked up signals from the downed EgyptAir Flight 804 black boxes. But the black boxes were extensively damaged when the plane, which was traveling from Paris to Cairo, plunged into the sea on May 19, killing all 66 people on board.

French and U.S. investigators have overseen the effort to extract information from the recorders. The recorders were made by Honeywell, a U.S. company. The plane, an A320, is made by Airbus, which is based in France.

The pilots made no distress call before the crash, and no group has claimed to have brought down the aircraft.

Nevertheless, while investigators have said it is too soon to determine what caused the disaster, a terror attack has not been ruled out.

That speculation is based on previous threats to the plane, the proximity of hundreds of maintenance workers to the plane at four high-risk airports in the 48 hours before the crash, and an odd trajectory recorded on the flight – as well as the lack of emergency warnings before the plane was spotted with a flash and a fireball.