(Seaside, OR)  --  An investigation is ongoing into a three-alarm fire that killed one person at a home in Seaside.  Firefighters responded to the home off South Columbia Street early yesterday morning to find the structure engulfed in flames.  Fire officials say crews later found the body of 69-year-old Stephen Scott Penwarden inside the burned home.  Investigators believe he was the only person inside the home at the time of the fire.  It's not yet clear what sparked the blaze.