Two chemicals were inadvertently combined in a container in a storage room today at Flagstaff High School, causing noxious fumes that can lead to respiratory problems.

The accident was described as limited to just a container in that room – not a big spill covering any large area of the campus – and it happened on an afternoon when students are routinely released early from classes.

Bob Orrill, battallion chief for the Flagstaff Fire Department, said the chemicals were potassium ferricyanide powder and hydrochloric acid. When combined, the chemicals can react to create hydrogen cyanide gas.

Four people (three adults and one student) were taken to Flagstaff Medical Center midday Wednesday for precautionary evaluation, according to Flagstaff firefighters, a hospital spokeswoman and Coconino County’s emergency manager.

Students in an adjacent room to the storage room were evaluated at the school as a precautionary measure.

The accident happened as teachers were cleaning up a storage room in preparation for summer break, said Karin Eberhard, a spokeswoman for Flagstaff Unified School District.

“The teachers that were doing this cleanup immediately put the toxic-spill kit on it,” she said, preventing any toxic gas from being formed before calling the fire department.

Emergency workers still determined those involved should be transported to the hospital.

A hazardous materials crew has isolated the spill, and an outside contractor will dispose of the chemicals.