Amy Smart’s indie movie’s already blowing up — well, almost — since filming is on hold right now after a real GRENADE was found on set! The bomb scare began when location scouts showed up early Friday morning in an Altadena, CA neighborhood to begin work on “Sister Cities” … which stars Smart and Alfred Molina. Director Sean Hanish tells TMZ that the scouts stumbled upon what looks like an old, rusted grenade … sitting in a driveway. They immediately called on-set fire officials.
