It happened on the River Mole near South Molton
A formal investigation is underway after the pollution incident.
The Environment Agency says the pollutant has been identified as anaerobic digestate.
A 5 kilometer stretch of the the river was impacted and they've calculated that 10,000 fish died.
They say they can't share any further details at this time.
Man questioned over attempted murder in Exeter
Victim suffers knife wounds
Devon heroes recognised in King's New Year's honours
16 community champions make coveted list
Devon darts star reaches quarter-finals of World Championship
Ryan Searle hasn't dropped a set yet
Kate Bush ‘heartbroken’ after friend lost at sea
Singer pays tribute to her 'dearest friend'
Police investigate unexplained death near Chudleigh
Body found on Christmas Day
Major Devon to London rail disruption
Month-long works begin
