UPI reports that cryptosporidium in the water supply has sickened more than 2,000 people in the city of Ostersund, in northern Sweden.

The source of the contamination is unknown.

It is feared 3,000 to 9,000 people may be infected.

A warning to boil tap water was issued Friday and renewed Monday.

Several members of Sweden’s biathlon team, training in Ostersund for an international competition in the city, have come down with symptoms.