MATHIS, Texas (AP) — Six people were killed and three others seriously injured in a head-on collision in south Texas, according to Texas state police.

A vehicle carrying four men was southbound early Saturday in the northbound lanes of Interstate 37 near Mathis, about 20 miles (32 kilometers) north of Corpus Christi, when it collided with a northbound vehicle carrying five people, according to Texas Department of Public Safety Sgt. Nathan Brandley.

All four men in the southbound vehicle and one man and one woman in the northbound vehicle have died of injuries suffered in the crash.

The three injured are all hospitalized in serious but stable condition condition, Brandley said Sunday, and the cause of the collision is still under investigation.