(CBS) —Despite the bitter blast, some schools stayed open Thursday.

And a fire alarm at Rolling Meadows High School couldn’t have sounded at a worse time, CBS 2’s Mike Parker reports.

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An experiment in the science lab went awry Thursday afternoon, triggering a smoke alarm. That caused the evacuation of some 2,000 students and staff out of warm classrooms.

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“It’s uncomfortable out in the cold, but we got everyone inside as soon as possible,” Ted Birren, director of school operations, tells Parker.

He estimates students were outside for about two minutes. It seemed a little longer to students who were displaced from gym period; they were wearing T-shirts and shorts.

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No injuries were reported.