COLFAX, Calif. (AP) — A major Christmas weekend storm caused whiteout conditions and closed key highways amid blowing snow in mountains of Northern California and Nevada, with forecasters warning that travel in the Sierra Nevada could be difficult for several days.

Authorities near Reno reported a 20-car pileup on a snow-blow highway where drivers described whiteout conditions.

A 70-mile stretch of Interstate 80 was shut Sunday from Colfax, California, through the Lake Tahoe region to the Nevada state line.

The California Department of Transportation also closed other mountain routes while warning of poor visibility and slippery conditions for drivers.