Lawton, Okla. — At least four people have died as a major winter storm blows across the southern plains. Snow and ice have caused hundreds of accidents in Texas and Oklahoma, and government buildings and schools shut down, with a winter storm warning in effect through Friday.

The four victims died in weather-related crashes in Oklahoma. Slick roads caused a 21-car pile-up in Tulsa Wednesday night that sent at least two people to the hospital. In Wichita Falls, Texas, icy roads caused cars to veer out of control and flip over.

Up to six inches of snow has fallen in Shamrock, Texas, making some roads too dangerous to navigate. One good Samaritan pulled a vehicle out of a ditch and almost caused another accident. Now officials are urging people to stay off the roads.

Tracy Terrill from the Oklahoma Department of Transportation said his crews started spreading salt on the roads on New Year's Day in preparation for the storm, but conditions can change quickly, within just a half mile.

The state has 220,000 tons of salt mix ready to deploy. But the storm is expected to move towards the northeast later this week.