Middle school principal Patti Bannister advised police that a message written in the girls' bathroom earlier this week said "I will blow up this school on 6-7-13."
The school is located at 300 Diablo View Lane.
According to Pike, a student told administrators about the message, which started an investigation into whether the threat was deemed credible.
Pike said the school has taken action to ensure that the campus is safe for students to attend Friday.
He said school officials notified police, took writing samples from students, briefed staff members and hired a private security officer.
Pike said police would search the school Friday morning and have a presence on campus throughout the day.
Parents and students were also notified by the school about the incident with an alert sent via email, Pike said.
Pike said police do not believe the threat is credible.
As of this afternoon, no students had been detained or named as responsible for the threat, he said.
There are five days of school left in the year, he said, and administrators are encouraging parents to send students to school.