SAN DIEGO — The van crash on a rural highway in far eastern San Diego County Friday left a Naval Special Warfare sailor dead and four other service members hurt, the U.S. Navy said.

The update came Friday evening, hours after the crash at around 10 a.m. on Interstate 8 near Jacumba Hot Springs, according to California Highway Patrol. Jacumba is on the border of San Diego and Imperial counties, just north of the U.S.-Mexico border.

Five sailors — a woman and four men — assigned to Naval Special Warfare units on the West Coast were riding home in a van from training at Camp Billy Machen in Niland, California, the Navy said in a statement. The driver crashed off the highway and hit a boulder for reasons that remained unclear Saturday.

Cal Fire San Diego crews and U.S. Border Patrol agents worked to pull sailors from the wreckage and get them medical attention as quickly as possible.

One of the sailors, a man, was pronounced dead at the scene. Four other sailors were taken to hospitals for treatment, including two in “critical condition” and two in “stable condition,” according to the Navy.

CHP said in a statement that it was investigating whether all the service members had been wearing seatbelts. The sailor killed in the collision was riding in a middle rear seat of the van.

Police did not suspect drugs or alcohol played a role in the crash.

As the San Diego Union-Tribune notes, the Navy describes SEAL teams as “the heart of the NSW force.” But it wasn’t initially clear if the sailors involved in the crash were SEALs or otherwise connected to one of the special combat teams.