So far, around 12 institutions in Devon and Cornwall have received a threatening email. Schools in Durham have also been warned.

A spokesperson for Devon and Cornwall Police said: “We are aware of a series of malicious communications to schools in Devon and Cornwall as well as across the country.

“Enquiries continue to establish the facts and forces are working together to investigate who is responsible.

“Police take hoaxes extremely seriously. They divert police resources and cause disruption and alarm to the public.”

The threats come after bomb scares at schools in Hertfordshire last week. They were deemed to be a hoax by police