By Keith Coffman
DENVER (Reuters) - Search and rescue crews were looking for three men on Monday who have been missing since a four-mile-long mudslide inundated a remote area near the Grand Mesa National Forest in western Colorado the day before.
Mesa County Sheriff Stan Hilkey said at a midday briefing that he viewed the area by helicopter and that the slide's debris field of timber, mud, snow and dirt was unstable, hampering rescue efforts.
"It's an understatement to say it's massive," he said.
The slide tore through an area outside the mountain community of Collbran, the sheriff said, adding that the slide started on U.S. Forest Service land and continued onto private property. The town of 700 people is 200 miles west of Denver
The disaster area, estimated to be two miles wide and 250 feet deep in places, was described by deputies on the scene as very unstable, the sheriff said.
The mudslide occurred after nearly a week of soaking rain.
A witness told of hearing a sound similar to that of a freight train, the sheriff said.
Hilkey said the missing men, whom he did not identify by name, went to the area on Sunday morning to investigate damage to irrigation canals by a rockslide earlier in the day, when the larger slide hit.
The three men - a county public works employee, his son and a third man - have not been heard from since, he said.
Hilkey said communication is limited on the remote mesa, with no cellphone service, and the hope is that the men escaped the destructive slide.
"Everyone on this mountain is praying for a miracle," he said.
The sheriff said the search for the men will include unmanned drone aircraft with heat-seeking equipment, and added that a hydrologist with the National Weather Service and a geologist with the U.S. Geological Survey will view the site by air to determine which areas may be safe enough for ground crews to enter.
Hilkey said he contacted authorities in Snohomish County, Washington, where at least 42 people were killed in a mudslide two months ago, and received "very valuable" information from them on how to undertake the search.
(Editing by Barbara Goldberg, Peter Galloway and Steve Orlofsky)