A school bus crash in Chattanooga, Tennessee, Monday afternoon killed at least five and injured at least 20 more, authorities say. It was unclear Monday night whether all of the dead were children. Police haven't determined what happened, but they say early reports suggest the bus hit a utility pole, flipped, and wrapped around a tree, reports the Tennessean. "Certainly speed is being investigated very, very strongly as a factor in this crash," said the police chief. The driver survived and was being questioned. The Hamilton County district attorney said five people died at the scene, but exact figures on casualties were still unclear. The bus was carrying 35 students from kindergarten through fifth grade, reports AP. (More bus accident stories.)