SACRAMENTO, Calif. (CBS13) – A Sacramento water park was evacuated Monday after people complained of respiratory problems.

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Twenty people — mostly children — were taken to the hospital.

Emergency crews from both Sacramento Metro and Sacramento City fire were called out to Raging Waters at Cal Expo after several people complained of breathing problems caused by a chlorine build-up in the wave pool.

“What we think happened is that there are two pumps: a primary pump and a secondary pump. And the primary pump stopped pumping for some reason and some liquid chlorine built up in the system and when the secondary pump turned on some chlorine was pumped into the pool. That’s when people started complaining of respiratory distress,” said Sacramento County Environmental Management Department spokesman Douglas Osborn.

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Some of the swimmers were treated at the park and others were taken to UC Davis Medical Center and Kaiser South.

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Investigators don’t think the Raging Waters staff did anything wrong. They’re giving them credit for handling the situation fairly well.

There’s no word yet whether the park will reopen on Tuesday.

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The park has been open since 1986 and was originally called WaterWorld USA.