California Highway Patrol press release: 

On July 10th 2017, at approximately 0944 hours, a 2004 Lincoln was being driven southbound on US-101 just north of Weott.  For reasons still under investigation, the driver allowed the Lincoln run off the west road edge down the embankment adjacent to the off ramp and collided with a redwood tree.  The Lincoln overturned and came to rest on its roof blocking the off ramp.  One of the passengers sustained fatal injuries and was pronounced deceased at the scene.  The driver was transported to St. Joseph Hospital where she was succumbed to her injuries.  Three additional passengers were also transported to St. Joseph Hospital with major injuries.  During the investigation it was determined all three rear passengers were not restrained. 

The US-101 southbound off ramp to Weott in addition to the southbound slow lanes were closed for for scene investigation. 
The names of the deceased as well as the two juvenile passengers are being withheld until notification to family members can be made.  Alcohol or drug use does not appear to be a factor in the collision. 

The California Highway Patrol, Redcrest Volunteer Fire Department, Miranda Volunteer Fire Department, Cal Fire, City Ambulance of Eureka, and Cal Trans all responded to the scene.  This collision remains under investigation by the Garberville CHP.