5 children sickened by 'cloud of chlorine gas' at Florida pool

— -- 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."