Health and safety experts were called in today after two teenage boys were found dead at a holiday apartment in Co Derry.
Aaron Davidson and Neill McFerron, both 18, from the Ballyclare area north of Belfast, are believed to have been poisoned by leaking carbon monoxide fumes.
A third boy, staying with the friends in the same partment overlooking the beach at Castlerock, Co Derry, was resuscitated by paramedics after he too was found unconscious.
Officials from the health and safety agency checked all gas appliances inside he flat in a bid to trace the leak.
Police also carried out their own investigations.
Postmortem examinations are due to be held and an inquest is expected later.
The pair were awaiting their A-level results, due out later this month.
The boy who survived last night’s tragedy is in a stable condition at the Causeway Hospital in Coleraine and is expected to make a full recovery.