The explosion is suspected to have been an accident. According to a preliminary investigation, a student had picked up an unexploded rocket, likely fired by the Lebanese Shiite militia Hezbollah, and put it in his backpack, reports The Jerusalem Post, among others.
The high school class was on a school trip in Manara, in northern Israel. A total of 19 people were injured in the incident; one died and two were seriously injured. Ten students and one adult are being treated in hospital, according to The Times of Israel.
The military says it is trying to find and secure any other unexploded ordnance in the area.