NOVOSIBIRSK, February 2 (RIA Novosti) - The yellow-orange snow that fell in a West Siberian region Wednesday contains no toxic substances, experts said Friday.

"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.

The Emergency Situations Ministry said traces of discolored snow were also discovered in two districts of the Tomsk Region in West Siberia.

A portable chemical laboratory was delivered to Tomsk from Moscow to analyze the substance contained in the snow.

The ministry also said yellow and orange snow fell in one district of the Tyumen Region, also in West Siberia.

The Federal Service for Hydrometeorology and Environmental Monitoring said yellow and orange snow that fell in Russia's three regions is not harmful to humans. The service also said the snow's nitrogen content was four times the norm.

Russia's Federal Space Agency said colored snow was not connected with rocket launches. The Tyumen and Omsk regions border on Kazakhstan, where the Baikonur space center, which Russia leases from the Central Asian country, is based.

"There have been no rocket launches since January 18," the agency's press secretary, Igor Panarin, said.