A student attacked nine people with a knife at a secondary school in Ostrołęka, in the Masovian Voivodeship, Poland, on Wednesday, also injuring himself. Polish media report, citing local authorities, that none of the injured are in life-threatening condition. Police have detained the nineteen-year-old attacker, and prosecutors are investigating the incident as attempted murder, according to TVN24. The motive for the attack remains unclear. Authorities later confirmed that the suspect possessed an explosive device in his backpack which narrowly avoided detonation. The incident has prompted a swift response from emergency services and a full investigation is underway.