(St. Helens, OR)  --  St. Helens police continue to look for a 13-year-old boy who's disappeared, and the boy's father and the father's girlfriend have been arrested.  River Casino Elder was reported missing on May 24th by his grandmother, who was recently awarded custody of the boy after he was removed from his father's custody.  Police believe 45-year-old Marvin Elder and his 34-year-old girlfriend, Tiffany Kelly, know where the boy is but are withholding the information.  The two were charged with interfering with a police officer.