Police are continuing to investigate an incident at Newtown High School which led to a lockdown at the site.
A full lockdown was put into operation at around 2.15pm and police called to the school premises in Plantation Lane.
Police said the incident related to a threat received by a pupil. There had been reports a knife had been involved, but police said the reports were not correct.
A police statement said: "Dyfed-Powys Police attended Newtown High School following a report that a pupil had received a threatening message on social media.
"As a precaution the school went into a short lockdown which has now been lifted. Enquiries into the source of the message continue.”
The lockdown was lifted at the end of the school day.