Investigators are subjecting the flight recorders from the EgyptAir jet which crashed last month to electrical tests before analysis can begin.
Egyptian air accident investigation sources told Reuters news agency it would take "lots of time and effort" to fix the two damaged recorders.
The flight data and cockpit voice recorders were retrieved this week.
It is still unknown why Flight MS804 crashed into the Mediterranean on 19 May, killing all 66 people on board.
The plane was flying from Paris to Cairo when it vanished from radar.
Investigators have said it is too early to rule out any causes for the crash, including terrorism.
The recorders are being tested in the Egyptian civil aviation ministry's laboratories in the capital Cairo, AFP news agency reports.
