ANTIOCH, Calif. (KGO) -- Officials say 34 children, were treated for minor respiratory issues after being exposed to a chemical at Antioch's Prewett Family Water Park Thursday afternoon.
At 2:29 p.m., emergency crews responded to reports of a child complaining of respiratory problems after swimming at the water park located at 4701 Lone Tree Way. The water park has a series of swimming pools and water features that recently began seeing large crowds after the school year ended.
The Contra Costa County Fire Department says a total of 34 kids were affected, so officials closed the Antioch public pool for the day. At least 17 children were transported to local hospitals and another 17 children were treated and released.
ABC7 News spoke with a witness who says he heard a child screaming and complaining that their throat was burning. Then, that set off a number of other kids who began vomiting.
Hazmat officials say the kids were exposed to high levels of sodium hypochlorite, which is another form of chlorine. It's more stable than regular chlorine, but the downside is that it is stronger and more toxic, especially if it is ingested and that is what set off the initial call.
Officials are investigating to find out how it was released. "A possible chlorine release or exposure into the actual water, we're not sure at this time. County hazmat is here on the scene and they're doing an investigation as to what was the actual exposure," Contra Costa Fire Inspector Lisa Martinez said.
Investigators are examining the automated chemical release system for any malfunctions, but so far they say there are no obvious signs to explain the exact cause.
Fire officials don't know if it was isolated to one pool or if it spread to other pools.
The puzzling part is there were high levels of chlorine, but it wasn't enough to cause the vomiting symptoms.
"We don't know exactly what happened. That is something that they will need to figure out," Michele DiMaggio from the Contra Costa County Health Department said.
The park will be closed on Friday.
34 children sickened at Antioch water park; cause still unknown