The Environment Agency has identified the source of the pollution affecting the Rivers Piall and Yealm in South Devon.

A spokesperson said: “We are supporting the work to stop the discharge and prevent further material from being washed down the river. “We have officers at different locations on the river sampling and assessing the impact.

“Fisheries specialists have been on site since early this morning assessing the impact of the pollution on fish and fish habitat.

“This was hampered yesterday by the lack of visibility in the river caused by the pollution.” More than 12 miles of watercourse have been affected - the River Piall, which enters the Yealm near Cornwood and then flows down to Plymouth Sound.