Three teenagers have been arrested after alleged online threats prompted closures at all schools in a Manitoba school division.

The Selkirk, Man.-based Lord Selkirk School Division said none of its 15 schools would open Monday after at least two threats of violence appeared on social media, meaning approximately 4,000 students received an unexpected day off.

An 18-year-old man, an 18-year-old woman and a 16-year-old boy, all of whom live in Selkirk, were arrested before the start of the school day Monday.

Police said they were not looking for any further suspects.

A superintendent with the school division said the closures were enacted to ensure the safety of students and staff.

“It’s a very difficult decision to make, but nothing trumps safety,” Michael Polinuk told CTV Winnipeg.