Thousands of residents in parts of Surrey and Kent have been advised to boil their drinking water over fears that it could be contaminated with E. coli.
Hundreds of homes in the Oxted, Redhill, Limpsfield, Godstone and Sevenoaks have been affected.
SES Water said the problem was found during routine tests and “our teams are working to investigate the problem and restore supplies to their usual high standards.”
In a statement, the water company said: "We are supporting our most vulnerable customers as a priority.
"We are very sorry to everyone who is being affected. Everything possible is being done to do further testing."
The level of contamination has not yet been confirmed and SES Water is still waiting for further test results.
People in the area have been told to boil their tap water before drinking, preparing food or brushing their teeth. Cooled boiled water should also be given to pets.
The E. coli bacteria is usually found in the intestines of humans and animals. Although generally harmless, some strains can cause serious illness including bloody diarrhoea and vomiting.
