Fallbrook, Calif. - Authorities investigated Thursday whether a medical emergency was to blame for a solo-vehicle crash that killed a Chula Vista woman on the Fallbrook stretch of Interstate 15.

The accident occurred on southbound I-15 south of Old Highway 395 around 8:50 p.m. Wednesday, according to California Highway Patrol Officer Jim Bettencourt.

Witnesses told investigators that a Toyota Camry traveling about 60 miles per hour veered to the right and crashed into a metal guard rail, Bettencourt said in a statement.

The Camry then went left and crashed into a second metal guard rail in the center divide, he said, adding that witnesses reported never seeing the Camry's brake lights come on.

"Since there was not significant damage to the vehicle, it appears the driver may have had a medical emergency prior to the crash," Bettencourt said.

However, the county coroner's office will determine the official cause of death.

The driver was identified as a 53-year-old Chula Vista woman. Her name was withheld pending family notification.