(CNN) -- Police cars and fire trucks surrounded Jefferson County Open School in Colorado Monday, as hazmat crews decontaminated students outside -- spraying them down, fully clothed, in cordoned-off sections under a blue tent.
Students coming in after recess had reported eye and skin irritations. Thirty kids and a teacher's aide were eventually treated for symptoms similar to an allergic reaction, according to CNN affiliate KUSA. A handful were taken to the hospital. The rest were evacuated to a church down the street.
The K-12 Colorado school remained closed on Tuesday as investigators tried to figure out what "toxic irritant" had been released on the playground.
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