A late-autumn snowstorm lumbered into the Great Plains on Monday, unleashing snow and fierce winds that turned roads to ice, reduced visibility to zero and jeopardized thousands of holiday motorists’ travel plans just two days before the official start of winter.

The storm was blamed for a fatal accident in eastern Colorado, where a guard and an inmate were killed when a prison van lost control along an icy highway. Eight other inmates and a prison employee were hospitalized with moderate to serious injuries, according to the Colorado State Patrol.

National Guard troops and sheriff’s deputies in the Texas Panhandle were called out on nearly 100 rescues after Interstate 40, a major east-west route, was closed Monday night from Amarillo into New Mexico. No injuries were immediately reported and several shelters were being set up, Oldham County sheriff’s dispatchers said.