Durham police said in a statement that the chemical was released around 2:45 p.m. at the downtown YMCA. The statement said 34 children and two adults were treated for non-serious injuries.
Authorities say the six children in serious condition were exhibiting symptoms such as vomiting, respiratory illness, and skin and eye irritation. Their injuries were not believed to be life-threatening.
Durham Deputy Fire Chief Chris Iannuzzi said there was a report of a leak in the pool's disinfection system, and a hazardous materials team was on the scene trying to determine how to stop it.