The superintendent of a western Minnesota school district said a threatening message was behind the decision to call off classes Thursday and Friday.

Superintendent Greg Schmidt did not disclose the nature of the message discovered Wednesday at Lac qui Parle Valley High School, but he said classes at the district's high school and elementary schools were called off as a precautionary measure to allow authorities to investigate.

The district, which serves about 800 students, is enhancing its security "to ensure the safety of students and staff," and changes will take place immediately, Schmidt said in a statement released Thursday afternoon.

The Lac qui Parle County Sheriff's Office is leading the investigation, and there were multiple officers on campus investigating Thursday. Sheriff Allen Anderson said there was a threat of "violence against the school" but didn't specify how the threat was made.

He said it was not related to a threat made by a student in January when part of a message that said "shoot up school on 02-28-2020" was written on a bathroom stall door at Lac qui Parle Valley High School. In a news release issued Feb. 3, the sheriff's office said the author of that message confessed, acted alone and that the school district no longer considered the matter a threat to students or staff.

"The student was removed from the school pending discipline and/or prosecution of the matter," the release said.

Notice of this week's closure appeared on the school district's Facebook page Wednesday night. The message said school officials and authorities were working to resolve an "issue which has come up," part of the posting read. The posting also asked parents and students not to call the school district for more details.

Classes are scheduled to resume Monday, Schmidt said. Friday will be a "virtual day," the district said.