Mystery as white foam appears on UK river where dead fish found

Dead fish have been found in the same part of a river where mysterious white foam appeared as experts work to discover the cause. The Environment Agency confirmed that officers are investigating "small dead fish and fry" - fry meaning baby or young fish - in an area of the River Thet in Norfolk, as "the pollutant is an unknown substance".

Specialist teams were sent to collect samples on Saturday to find the source of the pollution and prevent it from spreading further. Firefighters also attended and told people not to enter the river or allow their pets to swim in it. The Environment Agency said more foam could gather, but would have "little environmental impact as it dissipates".

Anglican Water said there was a "third party" involved in the investigation, and the foam and fish deaths were not from any of its "equipment or assets in the area".

The Environment Agency said it would wait until the pollutant had gone before it investigates the longer-term impacts.

It also attended an incident involving foam on the River Thet in December 2024, but on that occassion could not identify the source.

An Environment Agency spokesperson said: "Environment Agency officers are continuing to investigate the cause of a large volume of foam found in the River Thet in the centre of Thetford yesterday.

"Our specialist teams have collected samples, detected the possible source, and prevented any further discharge. There will be an ongoing investigation to try to ensure that this does not happen again.

"It is possible that we might see a second foam plume today and the foam will continue to travel down the river. It is still visible but will have little environmental impact as it dissipates."