SUNDANCE — At least three young men were missing and presumed dead Friday evening after an avalanche trapped them in Provo Canyon.

In all, as many as 15 snowboarders and snowshoers were caught in the slide near Aspen Grove, a few miles west of Robert Redford's Sundance Ski Resort.

Most of the victims were either able to dig themselves out or were rescued after the slide. However, search and rescue crews could not find three Utah County men, who were apparently trapped under the snow.

"It's extremely unlikely that they will survive," said Utah County Sheriff's Lt. Dave Bennett. "When the snow stops, it sets up like concrete."

At 8 p.m., crews called off the search for the missing boarders, ages 18, 19 and 20, due to the high winds and extreme avalanche danger facing rescuers.

"If they're still buried, their time's up," noted a bartender at Sundance's Owl Bar, as temperatures outside were expected to drop well below freezing overnight.

The sheriff's office plans to use a helicopter to drop avalanche bombs in the area today before deciding whether to send more search crews up this morning.

The missing three, who names were not released Friday, were part of a group of five snowboarders who took the brunt of the avalanche. The other two in the party, also from Utah County, survived after being rescued.

An 18-year-old was buried only to his armpits and was otherwise uninjured, while a 20-year-old, who was completely buried until rescued, was taken to a local hospital with a leg injury and hypothermia, Utah County Sheriff's Sgt. Dennis Harris said.

The slide occurred near the start of the Mt. Timpanogos summit trailhead, about a half-mile from the Aspen Grove lodge, a popular Brigham Young University alumni recreation site. The avalanche came down the Roberts Horn chute and swept up the 15 people, who were either in the avalanche chute or just below it.

The chute, about a half-mile long, is a common location for avalanches, but the vicinity is rarely, if ever, closed to backcountry enthusiasts.

"I don't know if we've ever closed it," Bennett said.

Utah County Sheriff Jim Tracy added: "This is a wilderness area. For those who use it, it's user beware."

Sheriff's officials said they didn't think the snowboarders caused the slide but that the cascade of snow started naturally from above.

In total, three slides came down the chute, but the first was likely the largest and probably buried the three snowboarders in anywhere from four to 14 feet of powder.