Officials say the chemical is likely industrially linked and SEPA is actively investigating to identify the source and assess impacts.

Officials stress the spill was avoidable and express concern over industrial linkage and environmental damage.

Public communications indicate an ongoing investigation to determine the source and broader ecological consequences.

SEPA is investigating potential pollution sources and the impacts, aiming to identify the source and assess effects on the ecosystem.

A chemical spill, believed to be caustic soda, entered the Knockando burn—a tributary of the River Spey—killing a large number of fish, eels, and wildlife over a two-kilometre stretch.

The incident struck during the River Spey’s peak fly-fishing period and follows a recent pollution event on another Spey tributary, as well as an earlier white paint spill into the Burn of Carron.

The pollution is described as one of the largest incidents seen in 36 years, intensifying concern about repeated pollution events around the Spey.

Spey Fishery Board director Duncan Ferguson says the pollution event ranks as one of the largest he has seen in 36 years, affecting about a 2 km stretch of the burn and potentially delaying salmon recovery for up to five years.

Ferguson highlights the two-kilometre affected area and the scale of losses as unusually large in his three decades of experience.

Fly fishers say the salmon population on the burn has been wiped out in the affected stretch, with recovery expected to take years.