A stream has turned a bright blue colour, prompting an investigation.
Canons Brook in Harlow, Essex, became discoloured over the weekend.
A farm nearby stated that this was not the first time this had occurred and that it was “extremely concerning” because the stream served as a source of water for crops and was frequented by children and pets.
The Environment Agency stated that it was conducting an investigation but had found no evidence of wildlife harm.
“It’s a really vivid blue, you can’t miss it at all, and if you follow the brook down, it goes as far as the eye can see,” Elliot Wollen, manager at Herts and Essex Community Farm, explained.
“Because this brook flows into the River Stort, it contaminates a large area with this unidentified substance.”