A helicopter search was launched for the missing climbers Saturday morning after they failed to return on time from a scheduled five-day ascent of the mountain.
Officials said searchers found climbing gear and detected pings from the climbers' emergency beacons at the 9,500-foot level of the mountain. Their last known location before that was at 12,800 feet on Liberty Ridge.
"All indications point toward a fall of 3,300 feet from near the party's last known location," said Mount Rainier National Park spokeswoman Patti Wold. "There is no viable chance of survival from such a fall."
The area where they fell is at the base of a steep rockfall, and it's possible that their bodies will never be recovered due to the dangerous, unstable terrain in the area, Wold said.
Crews started their search for the missing group in the Liberty Ridge area, on the northwest shoulder of the mountain, where the group was last heard from on Wednesday at 6 p.m. when they called in via satellite phone. At that time the party was at 12,800 feet with plans to overnight.
But as searchers combed the area by helicopter on Saturday, pings were located from all six of their emergency beacons at the base of a rockfall at the 9,500-foot level. There was no activity detected.
Searchers then spotted debris and climbing gear but no signs of life at the site. It is believed that the bodies of all six climbers are there, and it appears they fell about 3,300 feet down the face of a steep rockfall.
The search was called off for the day, and Wold said there is no way searchers can access the area at this time - or possibly ever.
"At this point there are no plans to put people on the ground at the site because of the ongoing hazards," Wold said. "As snow melts and conditions change potential opportunities for a helicopter-based recovery will continue to be evaluated. There is no certainty that recovery is possible given the location."
The climbers began their ascent on Monday and were due out on Friday but they never showed up, Wold said. They were scheduled to reach the summit of Mount Rainier on Thursday, with a day to climb down.
The group was made up of four clients led by two skilled climbing guides from Alpine Ascents International, which reported the party missing at 4:30 p.m. on Friday.
"This accident represents a horrific loss for our guide partners and the families and loved ones of every one of the climbers lost on the mountain," said Mount Rainier National Park Superintendent Randy King.
"The climbing community is a small one and a close one and a loss of this magnitude touches many. Our thoughts are with everyone affected by this tragic accident."
The loss of life would be among the deadliest climbing accidents ever on the peak in the Cascade mountain range. In 1981, 11 people were killed during a guided climb when they were struck by a massive ice fall on the Ingraham Glacier.
Alpine Ascents' director of programs, Gordon Janow, said he wasn't yet ready to release information about the six climbers.
Some 10,000 people attempt to climb 14,410-foot Mount Rainier each year, with about half making it to the summit. The Liberty Ridge area is considered one of the more technical and advanced routes on the mountain.