PASADENA, Calif. (AP) — Police locked down a school and searched students Friday after a report that a person was walking on campus with a handgun, but no weapon was found, officials said. One youth was arrested.

SWAT teams were sent to Blair International Baccalaureate School shortly before 9:30 a.m. after a faculty member reported that someone on campus had seen a man with a handgun, police Lt. Tom Pederson said.

"Very little description of this person was provided," he said.

One student reported that another was armed, Pasadena Unified School District spokeswoman Binti Harvey said.

As a precaution, all 1,200 students were confined to classrooms for hours as police searched the campus, formerly called Blair High School. Anxious parents waited outside for hours until their children began being released after 5 p.m.

Police handcuffed and detained a youth but would not say why. Pederson, who said police weren't sure whether he was a student, called him a "person of interest."

Blair East, an adjoining middle school, also was locked down; those students were released at midafternoon. Officials did not search off the campus.