Two people were transported to the hospital by ambulance after a hazmat situation at Kentridge High School.
A number of staff and students complained of feeling ill just before school was released, Puget Sound Fire reported around 3:30 p.m. Tuesday.
Firefighters and paramedics evaluated nine patients, and two were taken to the hospital as a precaution.
Hazmat technicians were in the building and conducted air monitoring.
The incident was in an isolated area, a Puget Sound Fire spokesperson confirmed to MyNorthwest.
While the source was undetermined, the building was safe to return to, the spokesperson added.