A child has died after an incident at St John Lloyd Comprehensive in Llanelli.
Officers attended the school after concerns were raised for the wellbeing of a pupil. He has since passed away in hospital.
His family has been informed and are being supported by specialist officers.
Dyfed Powys Police has released a statement saying: "The incident is not being treated as suspicious and there is no need for other parents to be concerned for the welfare of their children.
"Our thoughts are with the family and the school at this sad time.
"St John Lloyd is working with the local authority, the diocese and Dyfed-Powys Police in order to ensure pupils and staff are supported."