The Daldykan River in Russia, which flows through the industrial city of Norilsk above the Arctic Circle, changed from its usual blue-green color to bright red over the last couple of days. There is no official scientific report identifying a reason for the change, but two theories have emerged.

The first is that the red color comes from the large quantity of iron that occurs naturally in the ground in that region. The second is a chemical leak.

Norilsk is plagued by pollution from many nearby factories, and ABC News reports that Russia's environment ministry has said there may be a leak in waste pipes that belong to mining and smelting company Norilsk Nikel, owner of a local nickel factory. The