Japan's government is denying claims that hundreds of tonnes of dead fish washing ashore is linked to the release of treated water from the Fukushima Daiichi nuclear power plant.
It comes after 30 to 40 tonnes of sardines and mackerels were found washed up on the shore of Hokkaido's Hakodate fishing port on Wednesday.
Government officials have since denied reports from the Daily Mail which suggest the phenomenon is a result of the treated water.
The report states that dead fish have been washing up almost four months since the discharge of treated water containing small quantities of radioactive material into the Pacific.
Since the discovery of the fish, images have been widely circulating on social media along with Fukushima conspiracy theories.
"We are concerned about unsubstantiated information," a Japanese fisheries agency official told local newspaper Maincichi Shimbun. "There have been no abnormalities found in the results of water-monitoring surveys."
People living in Hakodate are being urged not to consume the stranded fish amid reports they were being taken to sell or eat.
"We don't know for sure under what circumstances these fish were washed up, so I don't recommend eating them," fisheries researcher Takashi Fujioka said.
One fisherman who spoke with Maincichi Shimbun said they'd "never seen anything like this before".
"It makes me wonder if the marine ecosystem is changing."
Some experts believe the stranded fish were chased by predatory fish to the point of exhaustion, however, no one has been able to confirm answers.
"The cause is unknown at the moment," local fisheries official Mikiune Fujiwara told the newspaper.
"We plan to sample the seawater at the site and examine it to uncover the cause."
