Russian emergency workers have flown to a Siberian region where smelly and multicolored snow fell earlier this week covering about 100 square kilometers (40 square miles), officials said Friday.
The snow, which fell Wednesday afternoon, was yellow, green and orange and had an oily texture and unpleasant smell, the Emergency Situations Ministry said.
Officials in the Omsk region, about 2,250 kilometers (1,400 miles) east of Moscow, had warned local residents not to use the snow for drinking or other purposes, and to keep domestic animals from it, the ministry said.
More than 27,000 people lived in the area where the snow fell, but no health problems had yet been reported, the ministry said.
"At the present moment, we cannot give explanations to the snow which is oily to the touch and has a pronounced rotten smell, and we are waiting for the results of a thorough test on samples," Omsk environmental prosecutor Anton German was quoted by ITAR-Tass as saying.
Local officials in Omsk could not be immediately reached for comment, the AP reports.
RIA-Novosti, meanwhile, cited an emergency official in the adjacent region of Tyumen, west of Omsk, as saying strange colored snow had fallen there as well.