(Portland, OR)  --  An arson investigation is underway into a fire in a Bethany neighborhood that's still under construction.  The fire ignited just after midnight yesterday morning near Northwest 169th Avenue and Catalpa Street, at a house being built by home builder Noyes Development.  It's the fourth time in as many months that someone has set fire to a house being built by Noyes.  Police believe a serial arsonist could be targeting the developer.