WALNUT CREEK (CBS SF) — A student at Las Lomas High School in Walnut Creek has been arrested Thursday after a loaded firearm was found in the student’s backpack, according to authorities.

The school received a call Wednesday morning saying that a student on the Las Lomas High School campus had a concealed weapon. School officials immediately contacted Walnut Creek police about the tip shortly after 11 a.m. The school is located at 1460 South Main Street in Walnut Creek.

The school resource officer was able to locate and detain the the student without incident. The student’s backpack was searched and a loaded handgun was found inside.

In an excess of caution, the Las Lomas campus was placed on lockdown at 11:20 a.m. until police were able to ensure that the campus was completely safe. The lockdown was lifted at 12:25 p.m.

The student was arrested for being in possession of a loaded firearm and taken to Walnut Creek police headquarters. The investigation into the incident remains active, police said. The student is not being identified due to the student’s age.

Anyone with additional information about the incident is asked to call WCPD Officer Rosenbusch at 925-256-3532.