More than 1,500sq km (570sq miles) in the Omsk region of Siberia experienced falls of the snow, which was also described as “oily” and “smelly” and fell over several towns.
Officials have said that chemical analysis is being carried out and Vladimir Gurzhey, an official with the civil defence ministry in Omsk, said on Russian television that the snow had four times the normal levels of iron in it.
Residents in the Omsk area, where some 27,000 people live, have been advised not to use the snow for any purposes or allow their animals to graze in it.
The television report also said that the strange coloured snow had fallen in the neighbouring Siberian regions of Tomsk and Tyumen.
