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BRIDGEVILLE (KDKA) — A mysterious odor prompted the evacuation of Chartiers Valley High School on Tuesday afternoon.

According to district officials, the students were already being evacuated after dust from construction work triggered a fire alarm.

While that was going on, the “odor was discovered in a limited area of the building.”

School officials say ninth grade students have been taken to the middle school, while the 10th, 11th and 12th grade students were evacuated to the primary school.

Police and fire officials are trying to find the source of the odor. Once they clear the building, the students will be allowed back inside.

Stay with KDKA for the latest on this developing story.