Two women were killed Friday morning when a car they were in went off I-66 in Fairfax County and slammed into a tree, according to Virginia State Police.

Juanita Ann Waller, 54, of Lanham, and Shyrel Scott-Waller, 53, of Chester, Penn. died around 6 a.m. after the car left the westbound lanes of the highway near the exit ramp for the Fairfax Parkway, police said.

The driver, Clarence R. Waller, 53, of Chester, was taken to the hospital with minor injuries, police said.

Scott-Waller was the driver’s wife and Juanita Waller’s sister, police said.

Fatigue appears to be a factor in the crash, which remains under investigation.

This item has been updated.