PHOENIX — About 20 students at a school near Phoenix were exposed to a prison crowd control gas after a training exercise on Wednesday, officials said.

Richard Franco with the Florence Unified School District said students at Florence Elementary School were on the playground a little before noon when they began complaining.

“Within a few minutes of them being outside, they started coming and reporting burning eyes and throats, things like that, from an unknown chemical of some kind that was in the air,” he said.

It is believed the students were affected by CS gas — similar to tear gas — which was being used in a crowd control training exercise at the Florence prison complex just a few blocks away, Andy Wilder with the Arizona Department of Corrections said. The gas was used outdoors and wind likely blew it over to the school.

Franco said all the students were brought inside. Between 20 and 25 students were evaluated at the nurse’s office by paramedics, but none were hospitalized.

“All those students were cleared,” he said.

Franco said the school switched to a rainy day schedule as a precaution, meaning no students would be allowed outside for the remainder of the day.

“Everything is fine,” Franco said.

KTAR’s Ashley Flood contributed to this report.

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