Bulgarian officials say a 16-year-old has been arrested after explosive devices they think could have been used for a terror attack were found in the high school student's home.

Deputy Prosecutor-General Ivan Geshev said Saturday that police in Bulgaria's second-biggest city, Plovdiv, conducted a search after the boy's relatives reported finding handmade bomb components.

Officers said they discovered multiple explosive devices, including a pipe bomb and a device filled with 14 kilograms (31 pounds) of nails. They also found an Islamic State group flag and Islamist literature.