Egyptian aviation investigators will finish on Monday repairing memory units from the black box recorders of an EgyptAir flight that crashed into the Mediterranean last month, a senior investigation official said.

Extracting data from the memory units of the Cockpit Voice Recorder and Flight Data Recorder from EgyptAir Flight MS804 should help the country's Aircraft Accident Investigation Committee explain why the plane went down on May 19.

The repairs will be complete "within hours" after which the committee will be able to determine how easy it will be to extract the data, said the official, who requested anonymity because he was not authorised to speak.

Both black box recorders from the Airbus A320, whose crash en route from Paris to Cairo killed all 66 people on board, were recovered from the Mediterranean last week.

Investigators said the devices were heavily damaged and needed repair before they could be transcribed.

If intact, the cockpit recorder should reveal pilot conversations and any cockpit alarms, as well as other clues such as engine noise. But crash experts say it may provide only limited insight into the cause of the crash.

The data recorder, provided its memory chip is in good condition, will offer investigators a greater chance of determining the cause.

The crash was the third blow since October to Egypt's travel industry, which is still suffering from the 2011 uprising that ended Hosni Mubarak's 30-year rule.

A Russian plane went down in the Sinai Peninsula in October, killing all 224 people on board in an attack claimed by Islamic State. In March, an EgyptAir plane was hijacked by a man wearing a fake suicide belt. No one was hurt. - Reuters