Some 50 people, some of them children, have required medical treatment after inhaling chlorine vapors at a pool in the northern town of Kfar Vradim.
Magen David Adom ambulance service says 23 of them have been taken to hospitals in light condition, suffering from breathing difficulties.
Police said some have reported stinging eyes and vomiting. It added that officers have detained a truck driver who had filled the chlorine tank.