Don’t connect drinking water pipes to the pipe for contaminated water from the treatment plant: That’s what happened in the Danish town of Køge in 2007 when at least 120 people fell ill.

Residents are once again being asked to boil water after 45 people reported diarrhea and severe stomach cramps. Inspectors are in the process of determining the source of the present contamination.

According to Berlingske Tidende newspaper, businesses and public institutions that use water in the preparation of food are also being contacted by regional food authorities for instructions on how to deal with the current situation.