* 2 adults and 40 children were hurt, 6 initially considered seriously.
* Sodium Hypochlorite, a chlorine compound often used as a disinfectant or a bleaching agent, was leaked
* The Y reopened at noon Thursday, but pool will remain closed.
* The patients have been released from the hospital after evaluation and treatment.
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The YMCA said though the facility reopened at noon Thursday, the pool would remain closed. YMCA officials are working with local authorities and maintenance crews to determine an appropriate time to reopen the pool.
The numbers of people affected fluctuated from initial reports of 23 hospitalized, to 42 and then 39 as multiple agencies worked to coordinate the scene and release information.
The children affected ranged in age from 6 to 12. After their swim, some campers complained about nausea and breathing issues. Some showed symptoms such as vomiting, respiratory illness, and skin and eye irritation.
The Durham Downtown YMCA was evacuated Wednesday after what a YMCA spokesperson initially called a "maintenance issue" and the Durham Fire Department called a reported chlorine leak. Durham FD later determined that Sodium Hypochlorite was the chemical that leaked, not chlorine. The incident "appeared to be a mechanical issue," and not a human error.
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The release of the sodium hypochlorite happened in an indoor pool.
The chemical is commonly found in bleach, water purifiers, and cleaning products. It used for everyday maintenance of swimming pools.
Breathing fumes may cause poisoning, especially if the product is mixed with ammonia.
Durham Deputy Fire Chief Chris Iannuzzi said the department responded to the call at 2:43 p.m. When firefighters arrived, they found evacuation of the pool area in progress. About 35-40 people - adults and children - were in the pool at the time.
Assistant Durham Fire Chief on how hypochlorite sparked evacuation of Downtown Durham YMCA today: pic.twitter.com/AUuwfRONlL— AngelicaAlvarezABC11 (@AlvarezABC11) August 3, 2017
The victims were taken to either Duke University Hospital or Duke Regional Hospital. By Thursday morning, all the patients had been released from the hospital.
"Duke University Hospital has had approximately 30 patients who have been evaluated and treated in the emergency department, and so far, there have not been any who have required admission to the hospital," a Duke Hospital spokesperson told ABC News via email. "Duke Regional Hospital has had about 10 patients evaluated and treated in the emergency department, and none of those have required admission to the hospital."
"Earlier this afternoon, a lifeguard at our Downtown Durham YMCA reported a strong chemical odor near the pool pump room," the YMCA said in a statement. "YMCA staff immediately contacted EMS. They, in turn, contacted the Durham Fire Department who determined that this was a hazmat situation."
There was a reported leak in the disinfection system, Iannuzzi said, and the hazmat team was called in to determine what leaked and how to "mitigate the situation."
Everyone was removed from the building at 218 W. Morgan St. The YMCA contacted parents who had children there to make them aware of the situation.
A tent was set up outside the YMCA, and Durham police and firefighters worked to evaluate people overcome by fumes.
About 100 campers swam in the Downtown Durham YMCA pool, the Y said. As part of their daily routine, they were taken back to their camp at Club Boulevard Elementary School.
"About 3 p.m., some children began complaining about breathing issues. Our camp staff immediately contacted EMS and began notifying parents," a YMCA spokesperson said.
"Tonight, we continue to focus on serving the children and families impacted by the incident," the YMCA said.