German police said five people were killed and others injured on June 29 in a shooting in a youth welfare facility in the northern city of Stade.
One person had been arrested, said a police spokesman who did not provide an exact death toll or further details.
Local public broadcaster NDR and tabloid Bild gave a death toll of five. Some reports said the shooting took place in youth centre.
Police said a major operation was underway in central Stade, a city of about 50,000 people, on the Elbe river, 50 kilometres (30 miles) west of Hamburg
"We ask you to leave the area and give it a wide berth for your own safety," they said in a post on X.
