SISTERS, OR -- Deschutes County Search and Rescue resume efforts, Monday morning, to find a hiker missing on South Sister. The Deschutes County Sheriff's Office says 38-year-old Gerald Derrickson reportedly reached the summit Saturday evening. He separated from his hiking partner during his ascent and failed to return to the trailhead as planned. 

DCSO deployed more than 20 volunteers to the mountain, Sunday, along with deputies, US Forest Service Officers, Air Link and a National Guard Blackhawk helicopter. Searchers spoke with numerous other hikers, but no one reported seeing Derrickson.