More than 100 fish are believed to have killed by sewage being discharged into a river in Somerset.
The Environment Agency was called to the "pollution incident" near Langport after numerous reports of dead fish from the public. Officers found sewage discharge in the water.
The pollution, thought to be from an agricultural source, has affected a 2km stretch of the King’s Moor Drain, near Long Load, upstream of Langport.
Pumps have since been turned off at the site to contain the spill.
The Environment Agency says an investigation is now underway.
“The pollution is suspected to have been from an agricultural source, but as yet a specific source has not been identified," a spokesperson said.
“The discharge, which was apparently responsible for the death of around 114 roach and 1 chub, is no longer occurring but our officers remain on site assessing the situation.
“We have switched off the pumps at Long Load pumping station to contain the pollution.”
Environment Agency South West tweeted: “We are now carrying out an investigation and assessing the impact on the King's Moor Main Drain.
“If you spot pollution please call our incident hotline number on 0800 807 060.”