Both the flight data and voice recorders failed 24 minutes after the plane took off from the Sharm el-Sheikh resort en route to Saint Petersburg, when it plummeted from the sky into the Sinai Peninsula killing all 224 people on board.
Cairo and Moscow initially dismissed a claim Islamic State (IS) jihadists downed the plane, but growing evidence it was attacked has prompted several countries to warn against travel to Sharm el-Sheikh.
On Friday, Russian President Vladimir Putin also ordered flights to the Red Sea resort halted, in a fresh blow to Egypt’s already struggling tourism industry.
Kremlin spokesman Dmitry Peskov told news agencies the measure did not mean Russia believed the crash — the worst aviation disaster in Russia’s history — was due to an attack, and the investigation continued.
The head of Russia’s emergencies ministry said Russian experts had taken samples from the crashed jet and were testing it for any traces of explosives.
But a source close to the investigation told AFP the black box data “strongly favours” the theory a bomb on board brought down the plane.
Another person close to the case in Paris said the plane had suffered “a violent, sudden” end, saying: “Everything was normal during the flight, absolutely normal, and suddenly there was nothing.”
Egyptian Aviation Minister Hossam Kamal and the head of the Egypt-led investigation into the disaster are due to hold their first news conference at 1500 GMT on Saturday, although the government warned it could be delayed.