The Environment Agency has launched a criminal investigation into river pollution in Newcastle after the Ouseburn was spotted foaming in Jesmond Dene.
The agency was called in last month to find the source of the pollution, which led city parks bosses to tell locals not to enter the water or let their pets go in either.
Urban Green Newcastle, the charity which runs Jesmond Dene, has confirmed that officials had found the substance responsible and were cleaning pipes to remove it. Warning signs have been put up to advise anyone using the park.
When the froth was first spotted in April, the agency said it was "highly likely" that the pollutant had entered the river through the surface water drainage system, which is designed for rainwater run-off, and asked people not to put anything down those drains that contains chemicals.
An Environment Agency spokesperson said: