It is a grim sight – and this blanket of dead herring has left the experts puzzled.

Millions of dollars of dead herring have been found in a fjord in Iceland for the second time in less than three months.

Some experts believe it is caused by a severe cooling in temperature caused by northerly winds; others claim it is because of a lack of oxygen as a result of a construction of a bridge.

The herring weighs an estimated 30,000 tonnes and is worth around $24million, reports the Daily Mail.

The Icelandic government is monitoring the situation after agreeing to fund research - the fishing industry is a massive part of the economy - but in the mean time the clean up is causing problems.

The rotten fish smell is making life a misery for nearby residents while tens of thousands of birds have also been drawn to the site.

A man surveys the scene as the dead herring washes up. Photo: AP
The herring are collected as part of the clean-up. Photo: AP

Latest From 7News

Australian fighter pilots will target Islamic State soldiers fleeing their Iraqi stronghold of Mosul, with coalition forces poised to assault the city in what looms as the toughest battle so far in …