CALIFORNIA BRIEFING

A 17-year-old boy with a sword, a chain saw and explosive devices was arrested Monday after he set off a blast at a Northern California high school, authorities said.

The boy detonated at least one of the devices at Hillsdale High School in San Mateo just after 8 a.m., said Police Lt. Mike Brunicardi. No one was injured.

The name of the boy, a former student at the school, was not released because he is a minor, authorities said.

After the blast, the 1,200-student school was evacuated and classes were canceled. Police initially received reports that someone was carrying a gun on campus, then subsequent calls of an explosion. Authorities did not find a gun.

Mary Kathryn Souther, a 15-year-old sophomore at the school, told the San Mateo County Times that she was in her history class when she heard a “huge bang.” Her teacher locked the door and told students to sit against the wall on the other side of the classroom, she said.