A large stretch of white foam which has appeared on a river is being investigated by the Environment Agency.
The thick foam is affecting the waterway along the River Thet in the centre of Thetford, Norfolk.
Its source has been detected and any further discharge has been stopped, according to an agency spokesperson.
Firefighters also attended and Norfolk Fire Service warned people not to enter the water or allow their pets to swim in or drink from the river.
The Environment Agency said it been on the site since 09:00 BST and had taken samples from the river.
“The foam is continuing to travel down the river and is visible,” a spokesperson said.
“We have detected the source and prevented further discharge.
“Our fisheries officers are attending site, and we would appreciate members of the public reporting any fish in distress on 0800 80 70 60.”
An Anglian Water spokeswoman said checks confirmed the foam had been caused “by a third-party” and was not from any of “our equipment or assets in the area”.
She added: “One of our managers is on site helping the Environment Agency with their checks which will then go back to the third party responsible.”
