More than 60 people were treated after an unknown chemical spilled in a pool area at a water park in the U.S. state of Texas, local authorities said on Saturday.

The authorities said the spill happened in Six Flags Hurricane Harbor Splashtown, a water park north of Houston. Hazardous Materials Management (HAZMAT) officials arrived at the scene to monitor the air.

The local fire department said over 60 people were going through decontamination and 31 were treated in hospitals. The people who were affected said they experienced minor skin and/or inhalation irritation.

Officials said they were unsure if the spill came from a chemical leak. HAZMAT crews were trying to identify the cause of the spill.