An anonymous male suspect was arrested by California authorities on Monday after an explosion at a high school in that state forced evacuation of students and cancellation of classes.

The blast -which sound was similar to a gunshot at Hillsdale High School in San Mateo, occurred after 8:00 am today, the San Francisco Chronicle reported.

No injuries were reported as the explosion happened outside a classroom.

While students evacuated, San Mateo police were searching from classroom to classroom to see if there were other bombs in the school, the paper noted.