Thousands of fish have died in a lake in Cheltenham in what the Environment Agency has described as a mass suffocation.
Pittville Lake is part of the town's largest ornamental park.
People are now being warned to stay away from the water.
Katie Rowlett reports:
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Elizabeth Martin was walking her pet chihuahua on a lead when they were set upon by a wolf-like dog.
Organisers MTV and Plymouth City Council are asking everyone to make sure they plan ahead for a fun, safe and hassle-free event.
It will be a bright start to the day with some showers. There will be a breeze.