The August 7 grand opening of Great Wolf Lodge in Webster, Texas, didn’t go as planned when improperly mixed pool chemicals forced the evacuation of the building and sent 16 people to the hospital.

Webster Fire Chief Dean Spencer said a third-party contractor mixed sodium hypochlorite and sulfuric acid, resulting in hazardous fumes.

The incident occurred in a pool house building located separate from the hotel and waterpark, and the victims of the fumes were hotel employees and contractors, including six construction workers from the Maldonado Construction Company.

Officials said that the Webster Fire Department “isolated the tanks, monitored the area, and confirmed no chemicals were detected in the hotel or waterpark.”

The situation was quickly contained and did not continue to affect the lodge’s operations that day.

Those affected were later released from the hospital.

Great Wolf Lodge issued the following statement: “The health and safety of our guests and pack members are always our top priority, and we greatly appreciate the quick actions of first responders from the city of Webster in response to the incident. We’ve received the all-clear to open the resort and all waterpark attractions.”