Russian metals giant Norilsk Nickel has admitted that a spillage at one of its plants was responsible for a local river turning blood red.

Russian environmental regulators had ordered an investigation last week into why the Daldykan River near Norilsk in the Russian Arctic had been discolored.

Despite initially denying that it was responsible, Norilsk Nickel admitted on September 12 that heavy rains on September 5 had resulted in water flooding over a "filtration dam" at the plant and into the river.

"Despite the short-term discoloration of the water...this incident does not present a danger for people or fauna in the river," said a statement from Norilsk Nickel, the world's largest producer of nickel and other major industrial metals.

But activists said it was too early to evaluate the environmental impact of the spillage as the official investigation was still ongoing.

The Norilsk region is one of the most polluted regions in the world. The country’s state statistics service classified the region Russia’s most polluted in 2010.

Based on reporting by AFP and BBC