Sixteen elementary school students in the German town of Coswig—in Saxony-Anhalt state—were taken to hospitals after round batteries were found in homemade cookies served at a school event, according to the Wittenberg district administration, Bild daily reported Thursday.

A total of 35 emergency services personnel, including a paramedic, rushed to the scene. One of the children was hospitalized by medical workers, while the other 15 children were taken to hospitals by their parents.

Police are investigating the incident.

Two batteries were found in the remaining cookies, a law enforcement spokesperson confirmed. It is not yet clear how they had ended up in the cookies.

There is no information also on the condition of the hospitalized schoolchildren.