Officers from the Environment Agency are at Savick Brook investigating a pollution incident.
Local resident Ruth Bond got in touch with Blog Preston after foam appeared in the brook in the Fernyhalgh Lane area, along with a strong smell of slurry.
Ruth said: “My husband discovered it this morning when walking the dog.
“There have been occasions recently, especially at weekends, where there has been a very strong smell of slurry coming from the water, but now we have what appears to be foam.”
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A spokesperson for the Environment Agency said: “The EA received reports of pollution in Savick Brook, Fulwood this morning.
“Environment Officers are on the scene and they are currently trying to trace the source. At least 3km has been affected, although no obvious harm to aquatic life has been observed.
“The pollutant appears to be cow slurry, however further investigation will confirm or deny this.”
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You can report incidents of this nature to the Environment Agency incident hotline on 0800 80 70 60.
Have you seen or smelt the pollution? Let us know in the comments below.