Police in Bulgaria's second-biggest city, Plovdiv, conducted a search after the high school student's relatives reported finding handmade bomb components, Deputy Prosecutor-General Ivan Geshev said. Officers said they discovered multiple explosive devices, including a pipe bomb and a device filled with 14 kilograms (31 pounds) of nails, as well as the IS flag and Islamist literature.
Geshev said investigators think the case involved only the teen and not an extremist cell or network in Bulgaria. The teen received instructions about explosive devices through the Telegram messaging app, as well as how to convert to Islam, the prosecutor said.
Psychologists were questioning the youth to establish his motives, but the initial investigation has not established any specific bombing targets for a possible attack. A July 2012 terror attack in Bulgaria resulted in six deaths.