A woman in the car was killed and a pregnant woman in the back seat lost her unborn child from injuries in the crash just before midnight Friday, state Highway Patrol spokeswoman Laura McPherson said.
A man driving the car and a child passenger also were injured and taken to a hospital. McPherson said the woman killed was Jeweline Ledbetter King, 49.
The SUV lost control on a curve on a two-lane highway, flipped on its side and crossed the center lane, slamming into an oncoming Ford Taurus. The SUV erupted into flames.
A passing motorist stopped to help, and used an all-terrain vehicle to pull the Taurus away from the burning SUV, McPherson said.
The bodies in the SUV were badly burned and have not yet been positively identified, McPherson said. The 15-year-old who survived the crash was ejected from the SUV and is at the University of Tennessee Medical Center.
Scott County High School Principal Bill Hall told The Associated Press on Saturday the four girls had attended a home football game earlier Friday night.
"We're all devastated," he said. "Our thoughts and prayers go out to their families and the other victims that were involved."
The crash occurred on U.S. Highway 27 in Scott County, which is northwest of Knoxville and sits on the Tennessee-Kentucky border.
Those in the other vehicle were from neighboring Fentress County, McPherson said. She did not know their conditions.
The crash shut down the highway for about eight hours.