Severn Trent is warning over 3,500 households in Derbyshire and Leicestershire not to use their water supply while it investigates the presence of high levels of chlorine.

The water company is asking customers in the DE11, DE15, DE65, DE73 and LE65 area of Derbyshire to not use their water supply as a precaution while it investigates a problem with higher than normal levels of chlorine at one of its service reservoirs in the Derbyshire area. Up to 3,600 customers could potentially be affected by Severn Trent’s request that the water supply should not be used at all.

The problem appears to be related to over-chlorination at  Severn Trent's Castle Donington reservoir which was picked up via an automatic monitoring system.

The firm has issued a statement apologising for the inconvenience this will cause, saying it is working hard to isolate the problem and get everything back to normal as quickly as possible. The water company is now working to flush the water out the system and constantly testing the quality of water at customers’ taps - Severn Trent is planning to have completed this work by midday tomorrow.

Severn Trent Water first tweeted about the problem four hours ago. It believes around 3,700 customer are potentially affected in total, and said it has been in touch with its most vulnerable customers to see what their needs are.