The cause is an operational disruption at the waterworks in Vänge.
Maria Lindqvist Pettersson, drinking water manager at Uppsala Vatten, says it is due to wear on a filter.
Municipal water in the town should not be used for cooking, drinking or brushing teeth. The request not to drink the water affects around 1,200 people in Vänge.
Water tanks will be available on Wednesday afternoon or evening.
Measurements have been made in several places, and the levels vary. Lindqvist Pettersson therefore does not want to say how high the levels were measured.
But in some places, the levels are significantly higher than the recommendations.
The health risk to anyone who has ingested the water is currently unclear; the Swedish National Food Agency is investigating. It is also not certain when the water will be drinkable again.
We will update the information tomorrow morning with the new status, says Lindqvist Pettersson.
She refers to Uppsala Vatten's website for ongoing updates.
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