Students and staff at Fort Frances High School returning from the holiday break were greeted with a police presence.
It is because of a bomb threat police learned about on Sunday.
OPP says the information provided to them was that a bomb was to be brought to the school on Monday.
Police say a youth was identified as a suspect and secured the school.
The first day of classes for the new year resumed as scheduled.
Police say staff and students should expect to see officers on-site for much of the day.
Anyone with information about the incident or who may have observed any suspicious activity around the school is being asked to contact police by calling 9-1-1.