A 25-mile-stretch along the coast of the Canadian side of Lake Erie has been hit with thousands of dead fish washing up onto it’s beaches. Scientists are looking into the cause of the mass kill-off and doubt that it would be because of a spill.

Authorities are also looking into whether the dead birds died as a result of eating the fish, or because of the same environmental hazard that killed the fish.

At the moment a natural phenomenon known as “lake inversion” is being put forward as the most likely explanation.

When a lake is “inverted” cold water, which carries less oxygen than warmer water because it is heavier, is found close to the surface where most of the fish are. The lack of oxygen causes the animals to suffocate.

Lake inversion has happened at Lake Erie in the past.