A Derbyshire school has been closed down for at least two days after bacteria was found in the water supply.
The contamination has affected one of seven tanks at Long Eaton Community School, but the head teacher said no children have been put at risk.
Dick Vasey said the water affected was only used in toilet cisterns.
"The health and well-being of pupils and teachers is paramount and we are not willing to put any students or members of staff at risk," he said.
"We have been cautious in closing the school down but we are taking the best advice we can get," he added.