A fire alarm at Hillview Middle School in Menlo Park on Monday afternoon (Feb. 27) that caused the entire school to evacuate was a false alarm, Menlo Park City School District Superintendent Maurice Ghysels said.

Mr. Ghysels said the alarm that sounded just before 3 p.m. was due to a "dirty detector" in the school's Building D.

Students and school staff all evacuated to the school's playing field until firefighters determined it was safe to return to the classrooms, he said.

"Maintenance is aware of the problem and will fix the detector," the superintendent said.

The school is at 1100 Elder Ave. in Menlo Park.