OKLAHOMA CITY (AP) - The Oklahoma Department of Transportation says whiteout conditions are slowing road-clearing efforts in western Oklahoma, where a blizzard dropped more than a foot of snow.

The department says all highways are closed until further notice in Beaver, Harper, Ellis and Woodward counties in northwest Oklahoma. All highways are also closed in Blaine, Beckham, Dewey and Roger Mills counties in western Oklahoma.

The department says low visibility is slowing work by crews that are clearing snow and applying salt and sand to roads.

Other road closures include U.S. 270 in Canadian County between Calumet and Geary, portions of northbound U.S. 283 in Harper County and portions of northbound U.S. 81 in Garfield County.