COLLBRAN, Colo. (AP/CBS4) — Rescue teams were searching Monday for three men missing after a half-mile stretch of a ridge saturated with rain collapsed, sending mud sliding for 3 miles in a remote part of western Colorado.

Ccounty road worker Clancy Nichols, 51, his 24-year-old son Danny and Wes Hawkins, 46, have been missing since Sunday after rain-saturated ridge collapsed.

The three went to check on damage Sunday from an initial slide near the edge of Grand Mesa, one of the world’s largest flat-topped mountains, after a rancher reported that his irrigation ditch had stopped flowing, Mesa County Sheriff Stan Hilkey said.

The search near the small town of Collbran has been hampered because only the lower third of the slide is stable. Even at the edges, the mud is 20 to 30 feet deep. It’s believed to be several hundred feet deep in some places.

“It’s an understatement to say it is massive,” Hilkey said. “It’s incredibly deep and full of debris.”

Hilkey said no signs of the men or their truck have been found. Their names haven’t been released.

“Everyone on this mountain is praying for a miracle right now,” he said.

VIDEO: Entire News Conference From Sheriff On Missing Men After Mudslide

Deputies estimate that the entire ridge had been moving for most of Sunday before someone called to report the slide at 6:15 p.m., describing it as sounding like a freight train. Hilkey believes runoff from Grand Mesa from recent rain triggered the slide. A hydrologist from the Natural Weather Service and a geologist from the U.S. Geological Survey were helping authorities assess the situation.

“The upper end of this is still unstable. It was still falling when we flew over it this morning,” Hilkey said. “We saw massive cracks in the hillsides that give us an enormous amount of concern.”

Bill Clark, a cousin of one of the missing men, visited the canyon where the slide struck and said it was completely filled with mud. He said the slide struck with so much force that some also spilled over into the neighboring draw.

“I’ve never seen so much earth move like that in my life,” he said.

From a distance of about 10 miles, the slide looked like a funnel, narrowing into a culvert below. It cut a giant channel through trees. The creek that once gradually flowed down the ridge now spurted down like a waterfall. Roads in the area, where some cattle grazed, were muddy from rain.

“How in the devil could this happen?” said Collbran resident Lloyd Power, gazing out at the slide.

He said residents were praying for the missing. “That’s all we can do,” Power said.

While the surrounding area is popular place for fishing, hiking and camping, the slide hit on land with an access gate that isn’t open to the public. No one else is believed missing and no homes were damaged. Energy companies were a monitoring oil and gas wells in the area, part of the productive Piceance Basin, but so far the mud has only come up to the edge of one pad operated by Occidental Petroleum Corp. The three wells there have been shut down, said David Ludlam, executive director of the West Slope Colorado Oil & Gas Association, a trade group.

Hilkey said he’d received a telephone call from authorities in Washington state, where a March 22 landslide swept a square mile of dirt, sand and silt through a neighborhood in Oso, about an hour northeast of Seattle. That slide leveled homes and killed at least 43 people.

– By P. Solomon Banda, AP Writer

(TM and © Copyright 2014 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2014 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)