Police cyber crime specialists are trying to identify the source of a mass bomb hoax which targeted schools across Scotland and triggered more than 300 calls to officers.
Threatening emails were sent to schools and nurseries across the country on Monday, with some buildings evacuated as a precaution.
Police Scotland has confirmed the messages are being treated as a hoax and said specialist officers and staff from its Cyber and Fraud Unit are carrying out “extensive enquiries” to establish where they came from.
The force said: “Police Scotland received more than 300 calls after threatening messages were sent to a number of schools across Scotland.
“These messages are being treated as a hoax. Officers and staff from Police Scotland’s Cyber and Fraud Unit are carrying out extensive enquiries to establish the source.
“For information about specific schools, contact the relevant local authority.”
Primary and secondary schools in areas including Glasgow, Edinburgh, East Renfrewshire, East Dunbartonshire, Inverclyde and elsewhere were among those affected.
Some schools were briefly evacuated while staff followed emergency procedures.
In Edinburgh, where pupils were off for an in-service day, staff were evacuated from several schools including Leith Primary, Fox Covert Primary, St Andrew’s Fox Covert Primary, Pirniehall Primary and Queensferry Primary.
Some teachers were later told to work from home.
In East Renfrewshire, where pupils had returned after the October holiday, the council said many primary and secondary schools received a malicious communication but continued to operate normally after speaking to police.
In Inverclyde, some staff were allowed to work from home for the remainder of Monday. The council said schools were expected to open as normal on Tuesday.
Renfrewshire Council also confirmed its schools would reopen as planned on Tuesday following the October break after police concluded the emails were a hoax.
The incident was not confined to Scotland.
Hundreds of schools in Northern Ireland were also sent threatening emails on Monday, with the Police Service of Northern Ireland saying up to 300 schools had reported receiving the same generalised threat.
The PSNI said the email it was investigating originated outside the UK.
Similar bomb warnings were also reported at schools in Hungary and Serbia on Monday, although authorities have not established whether the incidents in the different countries are connected.
Northern Ireland Education Minister Paul Givan said the threats there were not being treated as viable.
Police Scotland has not publicly confirmed that the messages sent to Scottish schools originated from the same source as those received in Northern Ireland.
The Scottish Government said it was aware of the incident and was working with police.
A spokesperson said: “We are aware threatening messages have been sent to a number of schools across Scotland and elsewhere in the UK. Police Scotland is investigating and treating them as a hoax.”