More than 60 people had to be treated on Saturday after a chemical incident at a Six Flags waterpark in Houston, Texas, officials said. 

The Harris County Fire Marshal’s Office tweeted that dozens of people experienced minor skin and/or inhalation irritation after a chemical incident was detected at one of Hurricane Harbor Splashtown’s attractions. The local fire department said that 26 people were transported to local hospitals and that 39 refused ambulance transport after a HAZMAT unit put people through a decontamination process. Roughly 4,000 people were at the park during the time of the incident. 

“Most of the patients that we saw during the time in the beginning were all respiratory distress, a little hard to breathe, things of that sort,” Spring Fire Department Chief Scott Seifert said Saturday at a press conference. “We didn’t see anyone with chemical burns, anything like that.” 

A three-year-old child, however, did have a “severe enough condition” that they had to be rushed to a children’s hospital, officials said. That child is now in stable condition. Officials said another woman appeared to be in labor when medical personnel arrived at the scene, but no further details were provided.

“At approximately 2:30 this afternoon, a small number of guests in a section of the park reported feeling ill with respiratory irritation,” a Hurricane Harbor spokesperson told CBS News. “The safety of our guests and team members is always our highest priority and the park was immediately cleared as we try to determine a cause. Out of an abundance of caution, the park has been closed for the day.”

The Fire Marshal said the last time it was inspected was June 29. The public health department also conducted an inspection of the pool facility in April. 

Officials said the leak was contained to just one attraction. Splashtown has 16 open attractions, according to its website. 

Officials said during the press conference that the chemicals they detected were a 10-13% hydrochloric acid — bleach — and 35% sulfuric acid solution. Bleach is often used to disinfect water in pools. Officials also said that when they tested samples of the water, it had a pH of 7, meaning it was in a neutral balance. 

“We don’t know exactly what happened prior that made people sick,” Harris County Judge Lina Hidalgo said. “…But something obviously went wrong.” 

Hidalgo added that they are going to be taking a look at the park’s “regulatory framework,” and officials said they are monitoring the air and water quality and investigating the cause of the incident.

There is “no indication of air quality or chemical leaks in the surrounding area,” Hidalgo tweeted.

The north Houston waterpark had just re-opened to all guests on July 3 after closing for the 2020 season due to the pandemic.