The McAuley Catholic High School remained open for classes on Tuesday after a Instagram post threatened pupils there on Monday.
The Doncaster school was threated on the social media site with a Google Maps image and a hashtag reading #McAuleySchoolMassacre, according to the Daily Mail.
The Instagram account and photo have been removed.
The threatening message is thought to have come from an account named 81daesh48 - Daesh being another name for the terror group Islamic State.
On Monday the school posted: "At this time pupils and parents are advised to not reply to any unsolicited emails or social media and to report anything of concern to the School/Police.
"A continued Police presence will be provided whilst the investigation continues and a Specialist Officer will be in school tomorrow should advice be required.
"At this time both the School and Local Authority, together with the Police see no reason to advise pupils to remain away from school and there is no information that would require the school to close."
South Yorkshire Police are no longer responsible for the investigation. Premier has contacted the South Yorkshire Terrorism Unit was told:
"We can confirm that police have received a report regarding potentially unauthorised and malicious posts made on a social media account.
"This information has now been passed to the North East Counter Terrorism Unit.
"Enquiries to establish the origin of this content are underway and the circumstances will be fully investigated."
