A number of pupils who fell ill at Pembroke School this afternoon are understood to have been in contact with 'legal high' substances, the Western Telegraph has learned.
Four emergency ambulances and the Air Ambulance had been called to the site.
A Dyfed-Powys Police spokesperson told the Western Telegraph: “At approximately 14:07 this afternoon, the ambulance service informed Dyfed-Powys Police of an incident they were dealing with at Pembroke Comprehensive School, where a group of pupils had become unwell.
"Officers attended the scene and established that a number of pupils were affected – some were treated at the scene and released, but others were conveyed to A&E in Withybush as a precaution.
"Air ambulance also attended as a precaution. None are believed to be in a life threatening condition.
"Enquiries have commenced into the circumstances, but early indications are that the group may have reacted to a type of legal high.”
A Pembrokeshire County Council spokesman said: “The school has launched their own investigation into the incident.”
A Welsh Ambulance Service spokesperson added: “Some pupils were treated at the scene whilst seven pupils have been conveyed to Withybush Hospital for a further check-up but none are believed to be in a life-threatening condition.”
“Though the cause is yet to be confirmed, it is believed the pupils may have reacted to an unknown substance.”