MUDDY CREEK TWP — The Beaver County woman killed in a car accident Thursday night apparently burned to death, the Butler County coroner’s office said.

Emily Hilliard, 21, of Rochester died after her car collided with an oncoming vehicle around 10:15 p.m. on Route 19, just north of Bauder Mill Road.

State police said Hilliard lost control of her vehicle before she crossed the center line and struck a vehicle driven by Susan Graham, 54, of Butler.

The impact of the collision caused Hilliard’s car to flip and roll down a more than 15-foot embankment.

“When the car flipped off the road and went down the hill, it caught on fire,” said Denny Trzeciak, a Butler County deputy coroner. “It was a tragic accident.”

Trzeciak said Hilliard’s car, which came to rest on its roof, was completely burned, adding the state of the vehicle made it unclear whether they’ll ever know what caused Hilliard to lose control of her vehicle. Trzeciak said he is unsure if an autopsy will be conducted.

A police report on the accident did not state whether Graham was injured.

Police are still investigating the accident.