(Portland, OR)  --  A death investigation is underway, after human bones were found by hikers along a trail in Southwest Portland.  Authorities say the remains were spotted yesterday afternoon on the side of a trail in the River View Natural Area west of Macadam Avenue.  Homicide detectives, forensic evidence criminalists, and the Oregon State Medical Examiner appeared on the scene and examined the area.  The state Crime Lab will put the bones under further examination.