The mill in International Falls is suspected as the source of an odour that forced an early evacuation of Fort Frances High School on Thursday.
Members of the Fort Frances Fire Rescue were called to the school at around 3 p.m.
The school had moved students to J.W. Walker School as a precaution.
The students were mainly from the intermediate grades as high school classes ended earlier with exams.
The Rescue Service says they later got similar reports from J.W. Walker and St. Mary’s.
Firefighters did searches of all three schools but found no gas leak.
They later learned the Packaging Corporation of America mill had conducted a pressure release at around 3 p.m.
It is believed the odour drifted in the direction of the three Fort Frances schools.
School officials at Fort Frances High were given the okay to go back into the building about an hour after the incident, allowing students to retrieve their belongings.
