The O-P-P Canine Unit made a couple of unannounced stops at two Sioux Lookout High Schools.
Paragon the police dog patrolled the halls recently of Pelican Falls High School and Queen Elizabeth District High School.
Police say they deployed the canine unit over concerns expressed by teachers about illegal drugs being brought to school by students.
Police say they found only small amounts of drugs during the sweep.
No one was arrested and no charges were laid.
Police warn students that future visits by Paragon are inevitable.