MOSCOW -- Strange colored snow that fell in three different Siberian regions is not toxic and may have been caused by dust and soils blown into the atmosphere from neighboring Kazakhstan, a Russian emergency official said Friday.

The snow, which fell Wednesday afternoon, was yellow, green and orange and covered more than 100 square kilometers (40 square miles) in at least three provinces, said Emergency Situations Ministry spokesman Viktor Beltsov.

Initial tests in three main cities in the region -- Omsk, Tomsk and Novosibirsk -- showed the multicolored snow was not harmful and he refuted earlier reports that said the snow was oily or foul-smelling.

He said it appeared the coloration came from clay and sandy soils common in northern regions of Kazakhstan.

"Preliminary results have found no dangerous chemical or radioactive materials," Beltsov said.

Officials in the Omsk region, about 2,250 kilometers (1,400 miles) east of Moscow, had earlier warned local residents not to use the snow for drinking water or other purposes, and to keep themselves and domestic animals from walking in or touching it.

More than 27,000 people live in the area. No health problems had been reported, the ministry said.