Parts of Siberia have been covered by black snow.
Those living in the town of Prokopyevsk say the phenomenon has allegedly been caused by a local coal processing factory.
Local media say other towns in the Siberian region of Kuzbass, which is home to 2.6 million people, have also been affected.
Parents have expressed concerns for the health of their children after schools and playgrounds in the region were seen to have several contaminated frozen patches.
The dirty snow is allegedly a result of coal dust from local coal plants mixing in with the snow.
Prosecutors in the nearby city of Kemerovo have reportedly started checking whether pollution standards have been breached by the coal industry.