Updated

Rescue crews searched Monday through the remnants of a deadly avalanche, unsure if more backcountry skiers were caught up in the slide near Whitefish Mountain Resort in northwestern Montana.

Sunday's avalanche tore down trees and left snow 20 to 25 feet deep. Two backcountry skiers were killed, and rescuers were pursuing reports that two others might have been caught in the massive slide. So far, no missing person reports have been filed.

Click here for photos.

Authorities cautioned rescuers faced difficult terrain and an avalanche zone that stretched a quarter mile across.

Click here for more from the National Avalanche Center.

"I don't know if we will be able to ever search that whole avalanche area," Flathead County Undersheriff Pete Wingert said, adding rescuers planned to look as long as they could.

Dangerous conditions delayed the start of Monday's search on Fiberglass Hill, a popular area on the opposite side of the mountain from the Whitefish resort about 210 miles northwest of Helena. Authorities said they used blasting techniques to remove an "unsafe snow mass" in the area of the avalanche.

Once the search resumed, some 100 rescuers used long poles to probe the snow every few inches to look for possible victims. Search dogs and a helicopter also assisted in the effort.

The search was halted for the night at about 7 p.m. but was expected to resume early Tuesday, Wingert said. The forecast called for high winds and snow after midnight.

Also Monday, authorities released the names of the two victims. They were identified as Anthony Kollmann, 19, of Kalispell, and David Gogolak, 36, of Whitefish.

Kollmann, who graduated from Kalispell's Flathead High School in 2006, was an upbeat student who loved to ski, according to DeAnn Thomas, director of the school's career center.

"He was well-liked, and he had a wide circle of friends," she said. "Anthony was really an outdoorsy kind of guy."

Kollmann was survived by his parents, Bob and Laurie, and two younger sisters, Amy and Ashley, according to family friend Courtney Heath, whose daughter, Darah, dated Kollmann for three years.

"We just loved him so much. He was just a phenomenal boy. He had the greatest little spirit," Heath said. "He stole my heart."

Heath said the family believed Kollmann was skiing by himself when the avalanche occurred, adding Kollmann skied nearly every day.

"He definitely died doing what he loved," she said.

Gogolak, who moved to Whitefish only recently, was with his brother-in-law when the slide began, according to the Missoulian.

The brother-in-law was partially buried and able to dig himself out, but Gogolak was lost beneath the slide, the newspaper said. His body was found about four hours later, buried in approximately 3 feet of snow and debris. He was not wearing an avalanche beacon.

On the mountain, witnesses were adamant they saw two other people caught up in the slide, said Sheriff Mike Meehan. As part of their search, deputies were checking cars parked overnight in the ski area to see if anyone was unaccounted for, Meehan said.

The cause of the slide remained under investigation Monday night, Wingert said.

The area where the avalanche occurred is U.S. Forest Service land, outside of resort boundaries, said Donnie Clap, spokesman for Whitefish Mountain Resort.

"We set off explosions to mitigate the [avalanche] risk within our boundaries," Clap said. "When you ski out of bounds, you are really taking your life in your own hands."

"We're just distraught over this tragedy," he said. "It's been really hard on all of us."

In Wyoming, three men were killed in an avalanche while snowmobiling Saturday in the Star Valley south of Jackson.

The Star Valley Search and Rescue team found the men's bodies in the Cottonwood Lake area. Authorities say Scott Bennett, Alan Jensen and Kim Steed were all from the Afton, Wyo., area.

Avalanches have killed at least 21 people across the West since Dec. 2, according to the National Avalanche Center. The national annual average for avalanche deaths is about 25. Thirty-five people were killed nationwide in avalanches in the 2001-2002 season, the most on record, according to the U.S. Forest Service.