Thousands of dead fish have washed up on a beach in northern Japan.

The fish, mostly made up of sardines and some mackerel, washed ashore in Hakodate on the northernmost main island of Hokkaido on Thursday, covering a stretch of beach about half a mile long.

Local residents said they have never seen anything like it and have been urged not to consume the fish.

The cause of the incident remains unknown, but Takashi Fujioka, a Hakodate Fisheries Research Institute researcher, suggested the animals may have become exhausted while being chased by larger fish.

He said a lack of oxygen while moving in a densely packed group could have led to them washing up on the shore.

The incident coincides with sardine migration southwards, Mr Fujioka said, adding that the fish may have suddenly entered cold waters.

Read more from Sky News:
Large volumes of dead fish ‘dumped’ by bottom trawlers
Deepest fish ever recorded revealed by scientists
Seafood sold in UK supermarkets may have a dark side

He said he has heard of similar phenomena before, but had never seen it in real life.

The decomposing fish could lower oxygen levels in the water and affect the marine environment, he said.

The day after the wash-up, city officials were seen inspecting the site and trying to collect the fish, while residents collected them to sell or eat, despite warnings not to.

Related posts:

Alleged drug kingpin told to hand himself in after being tricked into spreading fake phone app Italian woman’s body ‘found sitting at a table in her home’ two years after she died Macron admits ‘deep divisions’ in France as he scrambles to avoid political deadlock Eight doctors and nurses who cared for Diego Maradona face homicide charges Seven rugby players withdraw from match in protest over LGBT rainbow shirt Baby among dozens of children killed following British military action in Afghanistan Russia orders troops to withdraw from key city of Kherson ‘I have nothing to hide’: Man named in Farmgate scandal willing to testify over Ramaphosa buffalo deal Indian and Chinese forces clash on disputed Himalayan border Three of El Chapo’s sons charged over drug trafficking as US tackles overdose crisis ‘Concerning’ mutations in man’s bird flu infection Nepal earthquake kills at least 54 – with more deaths expected to be confirmed