(FOX 11) - A competitive swim team was sickened Wednesday evening during practice when they inhaled chlorine gas.
Nineteen children were exposed and twelve of them were hospitalized for respiratory issues, according to the Ventura County Fire Department.
The owner of the Daland Swim School in Thousand Oaks said the swim pump likely malfunctioned.
"There was a little bit of chlorine that was concentrated in there and when the pump clicked on it came out," owner, Leslie Daland-James, said. "It was scary for sure, my child was one of the ones in the pool."
Daland- James said her staff immediately called paramedics who began treating children on scene.
Several children were given oxygen to help relieve respiratory symptoms.
Captain Stan Ziegler described the symptoms as, "difficulty breathing and coughing and those kinds of things that would be related to the chemicals."
The children range in age from 11 to 15 years old and part of a competitive swim team, according to the school.
Daland-James said some of the children got out of the pool in distress and her staff helped them showered off the chemicals until paramedics responded.
"We have been in contact with the parents at the hospital and no one is critically injured," she said. "Their lungs are hurting a bit but they are going to be fine."
Daland-James said her son was also hospitalized and was given asthma medication to help him breathe until he was sent home.
She plans to close the school Thursday to make sure the pumps are in working order before reopening