BERLIN—German prosecutors said on Friday that they have launched formal investigations into whether two regional officials failed to properly warn residents ahead of last month’s floods that killed 141 people and injured hundreds more. Prosecutors in the western city of Koblenz said investigations so far had confirmed an “initial suspicion” of negligent homicide and negligent bodily harm against the regional administrator in nearby Ahrweiler county. At least 141 people died and more than 700 were injured in the Ahr valley on the night of July 14–15. Dozens more people died in other parts of western Germany and neighboring Belgium. A second member of the crisis management team, who was in charge of the emergency operation for at least part of the night, is also being investigated, prosecutors said. Residents of the flood-hit towns reported receiving little advance warning of the severe flood that occurred on the night, with some claiming …