About 200 students, along with faculty and staff were evacuated from Henry W. Longfellow Career Exploration Academy in Dallas due to a gas leak on Wednesday morning.
According to Jason Evans with Dallas/Fire Rescue, HazMat teams picked up readings for both natural gas and Carbon Monoxide in the building.
The school is located at 5314 Boaz Street and is part of the Dallas Independent School District.
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Everyone was let back into the school just before 11:30 a.m. on Wednesday.