Three Dutch water boards have stopped using the Maas river as a source of drinking water because of a chemicals scare, news agency ANP says on Wednesday.

A leak at a factory on the Chemelot industrial estate near Geleen in Limburg has polluted the river with pyrazoles, an organic compound which is released in the making of medicines and pesticides.

The chemicals entered the water via a defective purification plant and were identified during routine tests. Repairs are expected to take at least a week, the Chemelot organisation said in a statement.

Drinking water in Limburg is normally made up of 25% Maas water and 75% ground water. Until the purification plant is running normally again, local water companies will use 100% ground water in their products.

Edwin Hendriks, spokesman for the WML water board, said consumers can be sure their tap water is safe. ‘Information about toxicity shows that [pyrazoles] are harmless,’ he said. ‘They are just not the sort of thing you want in your water.’