A suspected pollution incident has killed a significant number of fish and other wildlife including eels and birds on a tributary of the River Spey.
A chemical, thought to be caustic soda, is understood to have entered the water at Knockando burn in Moray in recent days.
The Scottish Environment Protection Agency (SEPA) confirmed it is investigating a potential pollution incident on the burn.
Fly fishing anglers say the salmon population at the burn has been wiped out and could take five years to recover, with a 2km stretch of the watercourse "destroyed".
Duncan Ferguson, director of Spey Fishery Board, added that the pollution incident was one of the largest he had seen in 36 years of working on the river.
He said: "It's a tragic event. It's a really bad outcome and it didn't have to happen."
Read more from Sky News:
What is hantavirus? Global health expert explains
At least 12 wounded after party shooting
Mr Ferguson said the chemical is thought to be industrially linked.
The incident comes during the peak period for fly fishing on the Spey, and just 10 days after another pollution incident at another Spey tributary.
Earlier, a number of salmon died after white paint was spilled into the Burn of Carron at Aberlour.
A spokesperson for SEPA said: "SEPA are investigating a potential pollution incident in a tributary of the River Spey and are working to identify the source and impacts."
(c) Sky News 2026: Fish, eels and birds killed in suspected River Spey tributary pollution incident
King 'delighted' as Princess Eugenie announces she is expecting her third child
Woman and man die in Bristol explosion after 'domestic-related incident'
Peter Kay show bomb hoax suspect removed from court after outbursts during hearing
'Beautiful streaks': Eta Aquariids meteor shower to light up skies over Britain
Food price inflation still rising, as lower income households feel the squeeze, study says
Scottish soldiers prepare for NATO deployment to Estonia with urban combat drills
UK on verge of joining EU's £78bn loan for Ukraine as Starmer seeks reset with Brussels
Tens of thousands of cancer patients to benefit from one-minute NHS jab
