Initial examination of black boxes of Russian Metrojet flight 9268 denies the reports that it was shot down by a missile, claimed a source placed with the investigating team.
However, the act of terrorism has not been ruled out officially by investigators.
Earlier, Wilayat Sinai, an Egyptian-affiliated group associated with the Islamic States of Iraq and Syria (ISIS) claimed responsibility for shooting down the Russian passenger airlines, killing all 224 people on board, the Independent reported.
The claim, however, has been denied by the Egyptian authorities.
Even top American intelligence official James Clapper has expressed doubts over extremist group's involvement in the crash, though stating that a terrorist attack could still not be ruled out.
The frustration and anger mount among victims' families over opposing accounts by the various authorities.
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Holding a press conference in Moscow, Deputy Head of Metrojet Alexander Smirnov denied a technical snag as a possible cause of the crash.
An external impact on the plane could be the convincible reason behind the crash, he added.