A threatening email has been sent to a large number of schools in Northern Ireland, according to the Education Authority (EA).
It said the "message has similarities with a bogus threat sent last month" which was treated as a hoax by the Police Service of Northern Ireland (PSNI).
"At this stage, we have not been made aware of any evidence of any credible threat to schools," they said.
The Department of Education advised schools to remain open "unless otherwise advised by the PSNI".
Police said they are conducting urgent enquiries, and liaising with the schools in question about the latest incident.
In October, a number of schools closed after an email threatened that "an explosive device" was located within hundreds of schools in Northern Ireland.
The EA said it was "liaising with police on this latest message".
The PSNI said they had received reports of "a concerning email sent to a number of schools across Northern Ireland".
On Wednesday, Police Scotland said "threatening messages were sent to a number of schools in Scotland and across and the UK".
"These messages were immediately assessed and are being treated as hoaxes," it said.
The EA said that "schools are advised to be vigilant and report any suspicious activity to PSNI".
"We fully appreciate that any message of this nature is distressing and can assure schools, parents/carers and children and young people that we will provide a further update following engagement with police."
In a social media post, Alliance assembly member Paula Bradshaw condemned the "reckless bomb threats sent to schools this morning".
"Such actions are unacceptable, causing fear and distress among pupils, parents and staff. Please remain calm and follow official guidance."
