Rescuers scoured a remote part of western Colorado on Monday for three men missing after a massive mudslide that swept through the Grand Mesa National Forest Sunday evening.

Clancy Nichols, 51, a country road and bridge employee, his son Danny, 24, and Wes Hawkins, 46, had been missing since Sunday after the ridge of the Grand Mesa collapsed.

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

The mudslide was estimated at two miles wide, four miles long and 250 feet deep by the Mesa County Sheriff's Office.

"We're praying for a miracle right now," said Hilkey. "We hope that they might been stranded. We have flown the area and have not seen anything."

Hilkey said, "There's no doubt that the slide is tied to the runoff and the amount of rain." The area had been soaked by a week of steady rain.

According to Hilkey, who said he viewed the area by helicopter and that the slide's debris field of timber, mud, snow and dirt was unstable and had hampered rescue efforts.

Federal geologists were on the way to assist in the search Tuesday, and a drone with heat-seeking technology would be employed as well, authorities said.

No structures or roads were reported damaged in the remote, mountainous area located 200 miles west of Denver, but officials expected a more accurate assessment Tuesday.