"The work is being carried out in an uninterrupted manner. We expect that the main phase of the search will last seven days," Minister of Emergency Situations Vladimir Puchkov was quoted as saying by Efe news.
He explained that the search tasks were being hindered by aircraft fragments scattered across different areas, snow and difficult terrain.
Russian authorities didn't forward any hypothesis on the possible causes behind the crash but said that all lines of investigation were open.
The Russian media released images captured by a surveillance camera of the moment when the Saratov Airlines plane crashed on the ground on Sunday causing a huge explosion.
Onboard were six crew members and 65 passengers including three children.
Initially, authorities reported that all passengers were Russian citizens, but later said that there were two foreign nationals -- a Swiss and an Azerbaijani.
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