A TEENAGER has been arrested after a suspected ’sulphur bomb’ caused a school to be evacuated.
Dyfed-Powys Police said it has arrested a 17-year-old but are not treating the incident, that closed Builth Wells High School for most of Wednesday, as terrorist related "at this time".
Powys council has confirmed Builth High will remain closed on Thursday, however school transport will operate as normal for children travelling to Builth Primary School which is unaffected.
Local people said they understood the school fire alarms had been set off by a smoke or stink bomb that was set off as an end of year prank.
Police said around 20 people were exposed to a substance that caused causing breathing difficulty and nausea to those exposed to it.
Investigations are continuing and all three emergency services have been at the school since the discovery of the substances at around 11.15am on Wednesday morning.
Dyfed-Powys Police said: "Specially trained officers from all agencies attended the scene and conducted an assessment which has indicated the substance is not believed to be a danger.
"Around 20 people were exposed to the substance; they were triaged by Ambulance at the scene and deemed well enough to go home.
"We would like to reassure the community there is no wider concern for health or safety in connection to this isolated incident.
"A 17 year old boy has been arrested, he remains in police custody and the investigation is ongoing. Police are treating this as an isolated incident which is not believed to be terrorist related at this time.
"Health advice has been issued to all affected by this incident, and there is not a concern for the wider public. If anyone affected feels unwell but the problem is not a medical emergency, please call NHS Direct Wales on 0845 46 47 for advice and guidance."
Builth High School had earlier said the incident was caused by a suspected smoke/sulphur bomb.