MINTURN, Colo. -- The search has been suspended for a Chicago backpacker who hasn't been seen since Oct. 3 when he set out alone in the Holy Cross Wilderness Area.

Eagle County Sheriff Joseph Hoy, in conjunction with Vail Mountain Rescue, said the search would be officially suspended at midnight.

James Nelson planned a five-day backpacking trip in the Holy Cross Wilderness, southwest of Vail and was reported overdue Friday.

Led by the Eagle County Sheriff’s Office, Vail Mountain Rescue along with five other search and rescue teams worked in excess of 1,000 hours over four days, but, despite these efforts they didn't locate Nelson.

"The decision to suspend the search for James was very extremely difficult," said Eagle County Sheriff Joe Hoy. "Search and rescue teams have scoured all of the terrain that could safely be searched on foot, some of it searched several times, in addition to the extensive aerial search with no results."

"We are extremely grateful for the assistance provided by Colorado National Guard High Altitude Aviation Training Center, TriState CareFlight, Alpine Rescue Team, Mountain Rescue Aspen, Douglas County Search and Rescue, Summit County Search and Rescue, Garfield County Search and Rescue, and the Eagle Valley Religious Foundation," said Hoy.

Searchers will continue to search for clues on Nelson's whereabouts when they are called to the Holy Cross Wilderness Area on other missions. At an altitude of 9,000 to 14,000 feet, the Holy Cross Wilderness Area is made up of some the most rugged terrain in Colorado. Experts in the field discourage individuals from searching on their own.