Police in Fairfax County are investigating a deadly car crash early Monday.

The incident happened around 2 a.m. on Sully Road near Route 66, where a car and a tractor-trailer collided, police said.

The driver of the car was killed in the crash, police said.

Police have not released the identities of either driver.

Police are investigating what caused the crash. It is unclear if speeding or alcohol were factors in the collision.