An explosion in a three-story residential and business building in the German city of Cologne: Cologne Blast Caused by Bomb.

BERLIN (Reuters) - An explosion in a building in the German city of Cologne that injured up to 12 people Wednesday was caused by a bomb, German police said. “We are assuming it was an attack,” a police spokesman said. He said there were no indications of a motive and no warning was given.

Fire services earlier said the blast in a three-storey residential and business building injured up to 12 people, four seriously. N-TV television reported earlier that there was speculation the blast was an attack of some kind on a hairdresser’s shop.

UPDATE: Spiegel Online has photos. (Hat tip: Thom™.)

A possible “work accident?”

UPDATE: Here’s Google’s translated version of the Spiegel Online page; they report that the bomb may have been packed with nails.