05/26/2014 01:25 am ET Updated May 27, 2014

Colorado Mudslide: 3 Missing On Grand Mesa After Heavy Rains Spark Slide

A massive mudslide in western Colorado may have swept away three people on Sunday night, the Mesa County Sheriff's Department said.

The mudslide, which was 2 miles wide, 4 miles long and 250 feet deep in some places, was called in to authorities at around 6:15 p.m., The Denver Post reported.

"This slide is unbelievably big," Lt. Phil Stratton of the Mesa County Sheriff's Office said in a statement.

The person who called in the mudslide on Salt Creek Road, near Vega Reservoir, on the Grand Mesa "described hearing a noise that sounded much like a freight train that is attributed to the slide," the sheriff's department stated.

Heavy rains have fallen on Mesa County for most of the day, likely causing the slide.

Rescue teams have been dispatched to the scene to search for three residents who were reported missing in the slide area, 9News reported.

Road blocks have also been set up outside the mudslide's perimeter. The area is very remote, the sheriff's department stated, and no structures were damaged.

Deputies on the scene said the area was very unstable.

AP story continues below:

Clancy Nichols, 51, a county road and bridge employee, his son Danny, 24, and Wes Hawkins, 46, have been missing since Sunday after the ridge collapsed. They went to check on damage 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 and about a half mile wide.

"Everyone on this mountain is praying for a miracle right now," Hilkey said.

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.

Hawkins' cousin, Bill Clark, said he went along with Clancy and Danny Nichols to check on why an irrigation ditch had stopped flowing because he works for an area water district. He said he has a family and young children.

Clark, who visited the canyon where the slide struck, 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 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.