Five children were transported to the hospital in Tampa after a malfunction at a local indoor swimming pool caused a concentrated "cloud of chlorine gas" to form, according to the Hillsborough County Fire Rescue department. 
 
 The incident took place at around 7 p.m. on Monday, when authorities responded to a 911 call saying there was a chemical release at the Calypso Pool in Tampa. 
 
 "Five pediatric patients were transported from the scene to the hospital for evaluation after complaining of stomach discomfort and nausea after leaving the indoor pool area," the Hillsborough County Fire Rescue department said in a statement. The children had respiratory burns, stomach irritation and were vomiting, authorities said. 
 
 The owner of the pool told officials that a thunderstorm earlier that day caused a water pump at one of the indoor pools to shut off, leading to chlorine build-up in one of the pipes. When the pump started working again, "it pushed the chemical mix into the pool causing a small cloud of chlorine gas," according to the Hillsborough County Fire Rescue department. 
 
 A hazmat crew arrived and assisted in ventilating the pool area, and eventually determined the building and pool to be safe. 
 
 The Calypso Pool operators told ABC News in a statement that the incident was a "freak accident." 
 
 "We've trained hundreds of kids for water safety and our concern is about everyone's safety," the statement added. "We believe that it was a malfunction." ||||| - Hillsborough County Fire Rescue says it was called to the Calypso Pool on Bearss Avenue around 7 p.m. Monday after a chemical release caused several people to get sick. 
 
 Five children were taken to the hospital for evaluation after complaining about stomach discomfort and nausea. They were all inside the indoor pool area at the time. 
 
 The store owner said an early afternoon thunderstorm caused a breaker to trip on one of the two indoor pool pumps. He said the pump that circulates the indoor pool water shut off while a pump that infuses chemicals into the pool water kept running, putting approximately 2.5 gallons of mixed chlorine and muriatic acid into the pipe. 
 
 These chemicals set stagnant in the pipe until the breaker to the circulating pump was repaired. When the circulating pump kicked back on, it pushed the chemical mix into the pool, causing a small cloud of chlorine gas. 
 
 Hazmat crews were called to vent and test the building. It was later determined the pool chemicals were balanced and back within safety guidelines. The building was cleared of the chlorine smell, and released back to the owner.
– A scary moment at an indoor swimming pool in Tampa, Florida, this week: Five children had to be taken to the hospital after a cloud of gas formed. The Hillsborough County Fire Rescue responded to a 911 call from the Calypso Pool about a chemical release around 7pm Monday, reports ABC News. They transported the children, who were complaining of stomach discomfort and nausea, to the hospital, where they were treated for respiratory burns, stomach irritation, and vomiting. The owner of the pool said a thunderstorm earlier in the day caused the pump that circulates water in the pool to shut off, reports Fox News. The pump that infuses the water with chemicals kept running, however, filling one of the pipes. When the circulating pump turned back on, it pushed 2.5 gallons of mixed chlorine and muriatic acid into the pool, causing the gas cloud. A hazmat crew was called in to ventilate the pool and eventually determined it was safe. The operators of the Calypso Pool called the incident a "freak accident."