to bring your o2s to the command post. reporter: saturday around 2:30 p.m., the first signs park. a lifeguard was sick, and soon after that, more and more people began becoming sick. it came in so strong and so fast. reporter: steven morris and his 9-year-old daughter lea describe the frightening moments. i just started coughing, then my eyes swelled up. reporter: the exposure believed to have occurred in this shallow pool for children. many of the victims suffering respiratory symptoms. 31 people were transported to local hospitals, including a 3-year-old boy and a pregnant mother. officials tonight questioning how the chemicals, bleach solution and sulfuric acid, common at public pools, reached such dangerous levels. if you can have 60-plus people get sick, and your system doesn t catch it, then clearly something is wrong with the system. reporter: most of those