Press release from the California Highway Patrol:

At approximately 5:00 p.m., 28 year old Thi Khal Lam Nguyen of Germany was driving a 2003 Ford Ranger pickup westbound on SR-299, west of Lord Ellis Summit.  For reasons still under investigation, Nguyen lost control of the Ford Ranger causing it to roll over multiple times.  Nguyen was transported by ground ambulance to Mad River Community Hospital with major injures.   

DUI is not believed to be a factor and Nguyen was wearing her seatbelt at the time of the collision.  The California Highway Patrol is investigating this traffic collision.