President Vladimir Putin declared a state of emergency last Wednesday, several days after 21,000 metric tons of diesel leaked from a collapsed fuel tank outside the city of Norilsk.The pollution now risks running north into the Arctic Ocean.

Toxic fuel from 21,000 ton leak reaches pristine lake, bypassing floating booms, as rivers of diesel pollution cover-up is exposed.

The exact reason of the leak is yet to be established, but a statement from Norilsk Nickel company, which operates the site suggests it could have been caused - worryingly - by collapsing permafrost.