Four people were killed in a head-on collision Sunday afternoon on Highway 281 in North Texas.

The Texas Department of Public Safety says the accident was triggered by a vehicle that crossed the center line into oncoming traffic on Erath County, about 65 miles southwest of Fort Worth.

A southbound Volkswagen drifted into the northbound lane and crashed head-on into a Mercedes, DPS said.

The driver of the Volkswagen, Courtney Kay Smalley, 18, of Lipan, and passenger, Kimberly G. Peacock, 19, of Fort Worth, along with the Mercedes’ occupants, Matthew Lee Keith, 29, of Searcy, Ark., the driver, and passenger Tsanti C. Keith, 26, were all killed in the scene.

The incident is under investigation, as it’s not clear what caused the Volkswagen to drift across the center line.