CHICAGO (CBS) — Two men are recovering after surviving an explosion at a high school near Indianapolis.

Firefighters said the explosion happened in a boiler room on the second floor of Carmel High School, as a contractor and a maintenance worker were trying to re-light the heater Wednesday evening.

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Both workers were injured, and were taken to the hospital. Their conditions were not available.

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Students who were at school for various practices were not hurt, and were evacuated to stadium locker rooms, where their parents picked them up.

“At a school the size of Carmel High School, there’s always activities going on. So there’s probably different practices and such going on, but no children, no kids were near this,” Carmel Fire Department spokesman Tim Griffin said.

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The explosion damaged the roof and a mechanical room at the school.