As a manhunt stretched into a third day Monday for a suspect in a shooting on a Kentucky interstate that wounded five people and struck 12 vehicles, authorities vowed to keep up a relentless search as the stress level remained high for a rural area where some schools canceled classes.

Authorities have been searching a rugged, hilly area of southeastern Kentucky since Saturday evening, when a shooter began firing at drivers on Interstate 75 near London, a small city of about 8,000 people located about 75 miles south of Lexington.

With suspect Joseph A. Couch, 32, still at large, numerous area school districts canceled classes for Monday. State police Master Trooper Scottie Pennington, a spokesman for the London state police post, urged area residents to lock doors, keep porch lights on and monitor security cameras. The search was focused on a remote area about 8 miles north of London.