Democratic Unionist Party (DUP) assembly member Trevor Clarke has condemned the email.
“Whilst any threat must be taken seriously, it is important that alarm is not caused unnecessarily and the wording of the message does raise some questions,” he added.
“The message has also been shared online and is there is an understandable concern on the part of parents in particular.
“I want to reassure them and the wider community that I have spoken to police this morning, and they have opened an investigation.
“It is important that we follow any advice which the police give to school leaders.”
Social Democratic and Labour Party (SDLP) councillor Roisin Lynch welcomed the swift response from “police, emergency services and schools to reassure pupils and parents and ensure people’s safety”.
“No parent should have to fear for their child’s safety when sending them to school and no young person should have their education disrupted by threats of this nature,” she said.
“I would encourage anyone with information to cooperate fully with the police investigation.”
