DENVER, Colo. (AP) -- Mudslides from heavy rains caused "extreme damage" to a major interstate and left it blocked with piles of boulders and logs, Colorado transportation officials said Sunday, as forecasters warned of more flash floods in the coming days across the Rocky Mountain and Great Basin regions.
The flood risk was elevated for many areas of the West where recent wildfires burned away vegetation and left hillsides more susceptible to erosion, the National Weather Service said.
Interstate 70 in Glenwood Canyon, Colorado, was closed with no word on when it might re-open after being pounded by flash floods over a three-day period. Lanes in both directions remained blocked by debris that flowed out of the burn scar from a wildfire last year in the Grizzly Creek area.
The torrent of rocks that came tumbling down the canyon's steep walls smashed apart sections of the concrete roadway and sheared off a long section of steel guardrail, photos provided by state officials showed.
More rain was in the forecast for the drought-parched region, triggering flash flood watches for portions of Utah, Colorado, New Mexico, Idaho, Montana, Nevada, Oregon and Washington state.
I-70 is a major transportation corridor between the Rocky Mountains and the West Coast.
An approximately 46-mile (74-kilometer) stretch of the interstate was closed. Transportation officials advised long-distance truckers to detour north onto Interstate 80 through Wyoming.
Crews were still assessing damage late Sunday. They had been working to clear the highway since Thursday when another flash flood hit Saturday, forcing them to evacuate the area and causing even more damage.
"When we know exactly what the damage is, then we'll have a better idea" on when it could reopen, said Colorado Department of Transportation spokesperson Tamara Rollison.
"It's not just clearing the debris. There's also the damage," she said. "Our engineering staff have never seen anything like this before."
More than 100 people had to spend the night on the highway Thursday night, including nearly 30 who took refuge in a tunnel following the mudslides in western Colorado.
Mudslides also closed down Colorado Highway 125 near Granby and U.S. Highway 6 over Colorado's Loveland Pass. Highway 6 was reopened Sunday, Rollison said.
In Rock Springs, Wyoming nine adults and eight children received assistance after flooding on Saturday, the Red Cross said.