"Experts have established that the substances in the snow are not toxic, but the iron content in the snow samples was four times above the norm," the press service of the local emergencies situations department said.
A public warning was issued in West Siberia's Omsk Region Thursday after polluted snow, yellowed and oil-stained, fell over an area of about 1,500 square kilometers (1,000 square miles), affecting some 49 communities with a population of at least 27,000.
Local residents have been warned against melting the snow for water and stepping on it wherever possible, the Emergency Situations Ministry said.
Experts said it was too early to talk about the cause of the phenomena.
"Snow samples have been sent for further tests in labs in Moscow and Krasnoyarsk, and we have also sent an inquiry to Kazakhstan about the possibility of industrial pollution," an emergency service official said. Kazakhstan is located southwest of the Omsk Region.
