Colville Tribal Police have been searching for a 67-year-old Inchelium, Wash., man since last weekend, but have been unable to locate him.
Daniel E. Calhoun was reported missing on Saturday but may have been gone from his residence for as long as a week, police said.
His wife and granddaughter arrived at the RV where Calhoun frequently stays and found his truck, boat, keys and other belongings, said his daughter, Sarah Little.
Police, along with Natural Resource Enforcement officers, have searched the Inchelium area and portions of Lake Roosevelt reservoir on the Columbia River.
Foul play is not suspected, police said.
Anyone with information about Calhoun is asked to call tribal police at (800) 551-5800.