(Portland, OR)  --  An investigation is ongoing into the discovery of a person's body inside a home that was destroyed by a three-alarm fire in Southwest Portland.  Fire officials say crews responded to the house on Southwest Madison Street early Saturday morning to find the structure heavily involved in flames.  Crews extinguished the fire and later found a person's body inside the home.  Neighbors had previously told firefighters that no one was home when the fire broke out.  It's not yet clear what sparked the blaze.