Gardaí said in a statement on Wednesday evening: “As a result, a Garda investigation team was established in Carlow Garda Station. Members of An Garda Síochána have been in touch with all affected schools during the course of the day."

While some schools made the decision to close, reopening is a matter for each school board of management, said gardaí, adding that they would continue to support schools and provide guidance.

The threatening emails are believed to have been routed through another country and the credibility of the message is still being investigated. There was no advance warning.

Lines of communication have been opened at a senior level with the Department of Education and Youth, said gardaí.

High-visibility patrols have been in place throughout the day and will continue for the coming days in the environs of all 42 primary schools across Carlow.

Earlier, Superintendent Anthony Farrell confirmed that a number of primary schools in Co Carlow received threatening emails on Wednesday morning.

A garda investigation team has been established at Carlow Garda Station. Senior gardaí have also opened lines of communication with the Department of Education.

He continued: “There is a possibility this email will be followed up by a ransomware attack — I ask that you do not click any links in any follow-up email. Advise Carlow Garda Station instead.

“Targeted patrols, including armed patrols, are being carried out,” he added.

He continued: “There is a possibility this email will be followed up by a ransomware attack - I ask that you do not click any links in any follow-up email. Advise Carlow Garda Station instead. 

“Targeted patrols, including armed patrols”are being carried out.

Scoil Mhuire Gan Smál, an all-girls primary school on Green Lane in Carlow town, contacted parents and guardians at 8.19am to inform them that the school would not open.

The message stated that “we, like some schools in the area, have received a threatening email this morning”.

The email added: “In the interests of ensuring the safety and wellbeing of our school community, Scoil Mhuire Gan Smál will remain closed today.

“The safety of our pupils and staff is always our absolute priority. We are working closely with the appropriate agencies and will keep you informed of any further updates as information becomes available.”

Parents and guardians have been advised to follow updates directly from their schools and avoid sharing unverified information.

Among the schools that decided to close were Scoil Mhuire Gan Smál, the Church of Ireland Primary School, St Laserian’s Special School, Scoil Mhuire Lourdes in Tullow, St Fiacc’s NS, Ballyconnell NS, Rathvilly Primary School, Scoil Molaise in Old Leighlin, Askea NS, Rathmore NS, Drumphea School, and St Columba’s.

Students were either told not to attend or informed they would be sent home by 11am. The emails received on Wednesday morning were understood to have come from an “unidentified” source.

Local Fine Gael councillor and principal of St Joseph’s National School, Fergal Browne, said the email came from an unknown Gmail account and confirmed that schools were liaising with gardaí.

“There is an increased garda presence around the town. A generic email came around. God knows where it came from. The email detailed that there would be mass shooting in the schools,” said Cllr Browne.

He explained that he decided to keep St Joseph’s National School open after speaking with gardaí.

“We want to reassure all parents and guardians.These things happen unfortunately. It’s very upsetting for school staff and parents. We are being extra vigilant today and liaising with gardaí at all times.

“Unfortunately these things do happen. It’s an outrageous thing to happen. All schools have tightened up on this in recent years. We have to be vigilant but not under or over react. Garda advice is sacrosanct,” he told KCLR FM.

The principal added that once the immediate concern had passed, school safety measures would need to be reviewed again in the future.

No secondary schools are known to have received either of the emails.

In a statement, gardaí said they were “aware” of a “communication that has been sent to a number of educational establishments in Co Carlow today”.

Schools and members of the public who notice any suspicious activity have been advised to contact Carlow Garda Station on 059-9136620 or 999.