(Hermiston, OR)  --  Police in Hermiston are searching for a driver who fled a traffic stop on foot, leaving behind a grenade.  The Hermiston Police Department says officers pulled the car over just after midnight Monday, prompting the driver to allegedly exit the vehicle and run.  Police found the grenade while searching the car, along with some scales and packaging materials.  It's not yet clear if the grenade was active.  An investigation is ongoing.