A leak at a North Carolina YMCA involving chemicals used to disinfect the pool sent 42 people to the hospital and closed down the facility Wednesday.
The leak was first noticed around 3 p.m. at the Durham facility when a lifeguard noticed a strong smell coming from near the pool pump room and told other staff members.
Children began coughing from the fumes, including some in the pool at the time and some that had been exposed earlier and were now back at their day camp location, ABC News reported.
Six children were considered to be in serious condition after the exposure but have improved with treatment. Symptoms included vomiting, skin and eye irritation, and shortness of breath, especially for adults and children with asthma. Injuries were not believed to be life-threatening.
The leak was sodium hypochlorite, which was believed to have reacted with other pool cleaning chemicals present nearby, Fox News reported.
Fire officials said the leak likely originated from a mechanical problem with the cleaning system, ABC News reported.
All parents of children exposed to the fumes were notified, and the YMCA pool remains closed while the incident is investigated.