ANTIOCH (CBS SF) – The Contra Costa County Health Services department is continuing to investigate a possible chemical exposure at the Antioch Water Park that sickened 34 people Thursday afternoon.

Among those that fell ill after swimming in one of the park’s five pools, 17 were sent to the hospital and released that same evening, according to a spokesperson for the Health Services department.

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Fire crews first responded to the incident at the park, located at 4701 Lone Tree Way, around 2:30 p.m. after a child reported having respiratory problems.

Fire officials initially had said that 40 people were sickened and that 10 to 15 people were sent to the hospital.

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The health services department is still not sure what caused the illnesses. So far, the cause does not seem to be exposure to sodium hypochlorite, which is used to disinfect water, Health Services spokesman Randy Sawyer.

The park remained closed Friday due to the ongoing investigation.

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