Rescuers flew over the glaciers of Mt. Rainier National Park on Saturday looking for two guides and four hikers who haven't been heard from since Wednesday, when they were attempting to scale the fifth-tallest mountain in the Lower 48.
The searchers could see camping and climbing gear about 9,500 feet up the 14,400-foot mountain, but it was unclear whether the items belonged to the six missing climbers.
Three parks rangers were conducting a separate ground search, a park spokeswoman said. The names of the missing were not released.
Nearly 11,000 people attempted to reach the summit of Mt. Rainier in 2013, and in most years about half of those who try reach the top, according to National Park Service statistics.
About 200 people were on the mountain about this time last year, which is considered early in the climbing season. Some of the climbs on Mt. Rainier can be completed in a few hours, though most people take two or three days to reach the summit.
The climbers at the center of Saturday's search were reported missing Friday evening, when they didn't return on schedule. They were attempting the Liberty Ridge route, one of the toughest and deadliest ways up the mountain.
Last week the park service reported the Liberty Ridge route as being in good condition with soft snow on the ground during the day. Snow flurries passed through the national park late Wednesday.
The climbers were at nearly 13,000 feet on Wednesday night, when they radioed in to Alpine Ascents International. The Seattle-based guide company is one of three that operate on Mt. Rainier.
Since 1897, at least 89 people have died on Mt. Rainier during summit climbs, according to the park service. Forty-five search and rescue operations took place between October 2012 and September 2013, costing about $150,000, according to the park service.