Water bosses have allayed fears over pollution in the River Colne.

They said foul-smelling reddish sludge which appeared on a stretch running through Linthwaite and Milnsbridge was harmless.

And Yorkshire Water are working with the Environment Agency to ensure there is no damage to river life.

The incident was reported to the Agency early yesterday, after people noticed the reddish-brown sludge and the smell near Linthwaite.

It transpires that Yorkshire Water had been doing safety checks on Butterley reservoir above Marsden and had released huge amounts of water into the river through a valve.

YW spokesman Matt Thompson said: “The checks involving the valve were part of an extensive series of safety works we are carrying out on the reservoir.

“This is separate to our plans for the spillway at Butterley, which are the subject of a planning application.

“As part of the tests, our engineers opened a reservoir valve which has not been used for a long time. There was a lot of extra water released into the River Colne and we believe the force of the water stirred up sediment which had been in the river already and washed it downstream.

“The valve tests are now concluded and the sediment is being washed away. I can assure people it is completely harmless”.

A spokesman for the Environment Agency said: “We have been liaising with Yorkshire Water and have confirmed there are no pollution problems in the river”.

One of those who was concerned was Milnsbridge resident Isabella Oumeng.

She noticed the sludge as she walked her dog along the river bank and contacted the Agency within hours.

“I have lived here 13 years and have never seen the river looking like that.

“The water was red and there was a sludge floating along which smelled foul”.

The Butterley plans by Yorkshire Water centre on repairs to the historic spillway.

The water company insist remedial work is necessary but local campaigners have objected to their proposals.