HUNDREDS of fish have been killed by pollution in the River Calder.
Environment Agency officials and Yorkshire Water staff are now trying to discover the source of the pollution.
The dead fish, including trout and grayling, were found yesterday in a stretch of the river in Elland.
The Calder is regarded as one of the county's best fishing rivers and many anglers were dismayed to see the dead fish.
Russ White, of Greetland, said: "We went to a stretch of the river near Elland and were surrounded by dead fish.
"We walked up the river for about a mile as far as Copley and saw all these dead fish."
The Environment Agency confirmed there had been several reports of dead fish.
He said investigations were now under way to determine what caused the pollution. Water samples are being taken and analysed.
A Yorkshire Water spokesman said the stretch ran past the Copley water treatment works but it was unclear whether or not the plant had any part in the pollution.
