Russia`s FSB security service said on Tuesday it was certain a bomb had brought down the plane, joining Britain and the United States in reaching that conclusion.
Egypt has not yet confirmed that a bomb was responsible, saying it wants to wait until all investigations are complete.
It was not immediately clear what role the employees had at the airport, which is Egypt`s third-busiest, handling a vast number of charter and budget flights for tourists seeking sea and sun in the southern Sinai peninsula.
Since the disaster, many flights to and from Sharm al-Sheikh have been suspended, raising concerns that Egypt`s tourism industry, worth about $7 billion a year and still a pillar of the economy despite having fallen sharply in recent years, will be further ravaged.
Alexander Bortnikov, the head of Russia`s FSB, said the conclusion of Russian investigators was that a homemade bomb containing around 1 kg (2 lbs) of TNT had detonated during the flight, causing the plane to break up in mid-air.
"We can unequivocally say it was a terrorist act," he said.
Egyptian ministers, led by President Abdel Fattah al-Sisi, were meeting in Sharm al-Sheikh on Tuesday, with a news conference expected later in the day.
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