ST. LOUIS—A tornado that swept through southeastern Missouri before dawn Wednesday killed at least four people and injured an unknown number of others, authorities said.

Sgt. Clark Parrott, of the Missouri State Highway Patrol, said the death toll from the early-morning storm might rise as crews sift through the rubble of damaged and destroyed homes in Bollinger County, about 50 miles south of St. Louis.

In addition to the deaths, an unknown number of people were injured by the storm, which is part of a larger system that could spawn further twisters and hail as it moves through the Midwest and South on Wednesday.