Tennessee Highway Patrol Trooper Kay Peay said the driver who died was Lucy Briley, 26, of New Orleans.
She was driving the tractor-trailer toward Nashville just past Almaville Road when witnesses said she veered over into the opposite lanes, crossed the eastbound lanes and struck a tree line, Peay said.
"At that point, she was thrown out," Peay said.
Briley was not wearing a seat belt. The trooper did not know why she traveled into the opposite lane.
"There was no sign of alcohol or drugs," Peay said.
Emergency Management Agency operations officer Tim Hooker said the truck leaked about 30 gallons of diesel and about six gallons of oil. The hazardous materials spill was supposed to be cleaned up but posed no danger.