A Tucson high school on Thursday was on soft lockdown a day after an explosion blew up a toilet in a boys' restroom.

Firefighters responded to the explosion at Pueblo Magnet High School at about 2:15 p.m. No one was injured.

The explosion's cause was still under investigation.

The school was on soft lockdown Thursday, meaning students are able to move from class to class but not allowed outdoors on campus.

Extra monitors were to patrol the campus, checking for suspicious activity.