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BREAKING: Three Missing After Colorado Mudslide

Three people are reported missing after a mudslide in Mesa County, Colorado.

The mudslide was first reported about 6:15 p.m. MDT Sunday, the sheriff's office said in a news release.

Rain likely contributed to the cause of the slide, the sheriff's office said.

The slide occurred after a thunderstorm went through the area, Meteorologist Brian Lada said. At least 0.35 inches fell in Rifle, Colorado, which is to the north of Collbran.

It had rained most of Sunday in the area, according to MesoWest observations.

Plateau Valley Fire Department first responded to the area of Vega Reservoir on the Grand Mesa, east of Collbran. The mudslide is estimated to be about four miles long, two miles wide and about 250 feet deep in many places.

It was described as very unstable by deputies on scene, who they estimate an entire ridge has been sliding for most of today. A witness who called into Grand Junction, Colorado, dispatch, described hearing a noise that sounded much like a freight train that is attributed to the slide, the sheriff's office said.

"This slide is unbelievably big," Mesa County Sheriff's Lt. Phil Stratton said,

No structures have been reported damaged; a full assessment will be done after daylight Monday.

Memorial Day will be mostly sunny, but spotty thunderstorms are possible in the afternoon, Lada said.