A chemical which poisoned fish in a Highland river has been identified as one used for treating swimming pools.
Police said sodium hypochlorite has several uses including treating swimming pools
Workers at the Conon Salmon Fisheries Board raised the alarm after finding a large number of dead salmon and trout in the Alness River on Monday morning.
The dead fish were found near Inchlumpie, Ardross.
Northern Constabulary said on Thursday that analysis of water taken from the river has revealed the chemical to be sodium hypochlorite.
Police said it has several uses including treating water for use in swimming pools.
The force said it believed the chemical has now fully dispersed and does not pose a risk to anyone using the river.
However, the full environmental impact was still being investigated by police and Scottish Environmental Protection Agency (Sepa).
Police added that the effects on any fish taken from the river were not yet known and strongly advised that anyone receiving salmon or trout from anywhere other than a reputable source should not eat the fish.