Three people are missing including a county worker and his son after Sunday's massive landslide outside of the town of Collbran.
Emergency responders estimated the landslide is 3 miles long, a 1/2 mile wide, and about 200 feet deep in some parts.
Rescue workers have suspended search efforts for the missing men because of the possibility of another landslide in the area, officials said Tuesday. Officials are presuming them dead.
Aerial surveys over the area will continue, said emergency personnel at a press conference Tuesday.
Clancy Nichols, 51, a Mesa County Road & Bridges employee, his son Danny Nichols, 24, and Wes Hawkins, 46, the district water manager for the Collbran Conservancy District have been reported missing since Sunday.
The three men reportedly went to investigate an irrigation ditch that they feared might have been damaged by another landslide that occurred Sunday morning, officials said.
On Sunday evening, a second massive landslide happened in the area.
Locals described it sounding like a freight train.
Rescuers spent Monday searching for the missing men using a helicopter and unmanned aerial vehicles.
"We saw massive cracks in the hillsides that give us an enormous amount of concern," Mesa County Sheriff Stan Hilkey said. "There's still a gigantic mound of dirt that looks unstable that could cause a secondary slide to come down on the first slide."
Rodney Hewitt, who owns 30-acres near the landslide, said he knows the missing men and looked for them for an hour on Monday morning near his property.
"There's nothing [on the hillside] anymore," Hewitt said. "All the debris went down the mountain so [it's] unlikely they will find those guys."
No structures were reported damaged, and no major roads were affected by debris, according to the Sheriff's Office.
Hilkey said the landslide was mostly likely caused by runoff from the Grand Mesa. The area saw rainfall over the weekend, which he said could have contributed to the slide.
The landslide occurred on the edge of the Grand Mesa on a mixture of public and private land.
Jonathan White, a geologist brought in to help assess the situation, said landslides in the area are common.
“The type of landslide is unusually big," White said. "The perimeter of Grand Mesa, all the way around, is mantled by landslides. What’s unusual is just the size.”
Hilkey said energy resources in the area were also threatened by debris. He said energy companies had to bring in a bulldozer on Monday to try and clear a road for workers to access condensate tanks, which are used in natural gas production in a process known as hydraulic fracturing, in order to drain them.
*Note: This story will be updated as the situation changes.*