It happened before 10:30 pm Wednesday on Millerton Road near Winchell Cove Road.
Authorities have now identified the victim as 33-year-old Paola Pallares of Fresno.
Officers heard reports of a person walking in the middle of the road. When they arrived, they found Pallares, who had been hit by a vehicle.
The driver had left the scene.
Right now, CHP officers have more questions than answers.
"We don't know why she was out here walking on Millerton Road at this time. We don't know the other vehicle or what that vehicle was doing out here, and really, that's the question we have," said CHP Sgt. John Tyler.
Officers will review surveillance videos from nearby businesses to determine what led to the collision.
Millerton Road was closed off for about two hours while authorities investigated.
Anyone with information is asked to call the California Highway Patrol.