It happened as students were arriving at school for the day, Co-Principal Gil Compton wrote in a statement to parents.
The suspiciousness of the situation prompted school officials to clear students and staff from the quad area of the campus, where the trash can was located.
The trash can was removed from the quad and taken a safe distance to the far perimeter of campus, according to Compton, at which time students and staff were permitted to return to the area and classrooms.
"With further investigation of the contents of the trash can a small electronic circuit was found. It seemed to be the inside of a toy or phone that was discarded," Compton stated.
"One thing we have been preaching to the students is to throw away your trash. The message must be getting through. It appears no ill intent was at play and all students and staff handled the situation perfectly."
It was not clear if police were called to evaluate the item.
Deputy Albert Martinez of the Riverside County Sheriff's Department told Patch there was not a record of Temecula police responding to the campus during the approximate time that it was reportedly discovered.