SAN CLEMENTE, Calif. -- An 18-year-old woman died Sunday when the SUV she was riding in rolled over and smashed into a guard rail on the freeway across from Camp Pendleton, authorities said.

The accident was reported at 2:06 a.m. on southbound Interstate 5 on the Las Flores Creek Bridge near Las Pulgas Road, according to a dispatcher with the California Highway Patrol.

The Camp Pendleton Fire Department pronounced the woman dead at the scene.

The driver, also an 18-year-old woman, was taken to Mission Viejo Hospital with moderate injuries, the dispatcher said.

No other vehicles were involved in the crash.

The two women were the only ones in the Ford Explorer at the time of the crash.

A cause has not yet been determined, the dispatcher said.