A shrapnel-filled pipe bomb exploded in a doorway of City Hall in Spokane, Wash., hurling 3-inch nails more than a block away into a park. It was the Spokane Valley's third bombing in less than a month. The building was unoccupied and no one was injured, officials said. No one immediately claimed responsibility, and police found no notes or other written materials with the debris. It wasn't known whether the blast was intended to divert attention from some other crime or was related to bombings April 1 at a newspaper office and bank in Spokane.