The Monday morning slide sent 100-ton boulders onto a viewing area to see Agnes Vaille falls in Chalk Creek Canyon below Mount Princeton, a 14,197-foot peak. Five hikers were killed, and a teenage girl was left with a broken leg and other injuries. She was rescued and flown to a Denver hospital.
Witnesses said some of the boulders were the size of cars.
Rescuers planned to wait until Tuesday afternoon to remove the bodies of the five who were killed, said Chaffee County Sheriff's department spokeswoman Monica Broaddus. Engineers from the nearby Climax molybdenum mine were headed to site to advise on safely getting the bodies out.
The recovery was called off Monday evening because rocks continued to shift when the coroner counted the fatalities, Broaddus said.
"The conditions are considered unstable," Broaddus said.
There was no immediate identification of the victims or whether they were a single group. A female hiker who heard the slide ran down the trail and called for help, said Chaffee County Undersheriff John Spezze.
The area had a rainy summer and a recent snowfall, said Spezze. It was too soon to know whether the weather prompted the slide, which left a football-field-sized gash in the mountainside, he said.
"It was totally unexpected. It caught everybody by surprise," Spezze said.
The trail is one of the first hikes recommended to people new to the area and is also popular with tourists, said Margaret Dean, a regular hiker who has hiked the trail with her 7-year-old grandson.
Dean, a copy assistant at The Mountain Mail newspaper in Salida, said the trail is easily accessible and provides a view of the falls and the Chalk Creek Valley in the Collegiate Peaks, which contains many mountains over 14,000-feet tall.
Agnes Vaille, the waterfall's namesake, was a Denver mountaineer who died in 1925 while attempting a difficult winter climb of Longs Peak, elevation 14,259 feet.
The U.S. Forest Service maintains the trail. Spezze said officials have asked the Forest Service for a permanent closure.
The Forest Service says the trail got medium to heavy usage. The trailhead lies across from Chalk Lake campground and is near the St. Elmo ghost town, a popular stop for tourists in Colorado's central mountains.