BERLIN, Germany (CNN) -- Investigators in Germany have arrested a 24-year-old man on terror-related charges. Authorities arrested the man "on suspicion of spreading al Qaeda propaganda online and for procuring materials which could be used to make a bomb," prosecutors said Friday in a written statement. Searches of a flat in Offenbach, Germany, and a business in Frankfurt, Germany, turned up a small amount of an "explosive substance" and a home-made electronic device. An initial assessment suggests that the items "could be used to ignite explosives," prosecutors said. The man holds dual German-Turkish citizenship, they said. The statement from prosecutors...