Environment Agency staff are looking into how thousands of fish died in a canal in Middlewich, Cheshire.

About 5,000 fish, including carp, roach and gudgeon, have been found dead in the Trent and Mersey Canal. A half-mile stretch of the canal, between Town Bridge and Big Lock, is affected.

First reports on Friday were of a smaller number of dead fish. But the full extent of the fish kill has now become clearer. A clean-up of the dead fish is being organised by British Waterways.

So far no obvious cause of the fish deaths has been found, but an Environment Agency investigation is continuing. Water samples will be analysed and post-mortems will be carried out on some fish in a bid to discover how they died.

John Ellaby, of the Environment Agency, urged anyone who may know what killed the fish to get in touch.

“Whatever killed these fish has left no obvious trace,” he said. “It is a tragedy that this canal, so popular with anglers, has been affected in this way. There was a major boat festival on the canal at the weekend, and if anyone has any information that could help solve the mystery they should contact the Environment Agency.”

Anyone who can help the investigation should contact the Agency’s free 24 hour emergency hotline on 0800 80 70 60.