LODI (CBS13) — Two drivers died Sunday morning after a head-on crash on Highway 12 in Lodi, California Highway Patrol Stockton said.

The crash happened at approximately 4:30 a.m. on the highway near Guard Road, CHP said.

Authorities said a red Nissan Altima was traveling eastbound on the highway while a gray Nissan Sentra was moving westbound in the same area. CHP said the Altima, for unknown reasons, entered the westbound lanes and crashed into the Sentra head-on.

CHP said both drivers were pronounced dead at the scene and were the only occupants of the vehicles.

Investigators said drugs or alcohol appear to be a factor in the crash.

The identities of the deceased have not yet been released.