Later in June, three people were taken to the hospital following a “possible hazardous materials incident” at the Asheville Racquet Club swimming pool in North Carolina.

The fire department said that the people reported having “difficulty breathing and difficulty speaking between breaths.”

Although eight total people were impacted, only one adult and two children were taken to a hospital for additional evaluation.

At the time, the fire department was unable to confirm the cause, but the department said they believe the reaction may be related to muriatic acid and chlorine.

In an emailed statement to McClatchy News, the Asheville Racquet Club stated, “We experienced an isolated incident on Saturday afternoon which unfortunately affected some of our swimmers. After an initial investigation in collaboration with internal and external resources, we have implemented measures to ensure that this type of incident cannot happen again.”