Environmental regulators say they have ordered an investigation into why a river in far northern Russia turned an alarming hue of red in recent days.
The Ministry of Natural Resources and Ecology said in a statement on September 6 that residents in districts near the industrial city of Norilsk had lodged formal complaints about the apparent pollution that fouled the Daldykan River.
"According to preliminary information, the possible reason for the river pollution may be a rupture in a slurry pipeline at a Norilsk Nickel plant," the ministry statement said.
Photos that circulated on Russian social media showed sections of the river that more resembled a stop light or a firetruck.
Norilsk Nickel, which is the world's largest producer of nickel and other major industrial metals, said it had seen the images but said there was no evidence of any leak.
The Norilsk region is one of the most polluted areas in the world. The country's statistics service classified the region as Russia's most polluted in 2010.