A search was underway for three children who were unaccounted for after their three siblings and parents bodies were found in the wreckage.
"We have every indication to believe that all six children were in there," Mendocino County Sheriff Tom Allmon said, appealing for tips to retrace where the siblings and two parents had been before the vehicle was found Monday in rocky ocean. "We know that an entire family vanished and perished during this tragedy."
The California Highway Patrol identified the adult victims Wednesday as Jennifer Hart and Sarah Hart, both 39. The agency said the family's SUV was driving Monday on the Pacific Coast Highway when it pulled into a dirt turnout and continued driving off the cliff.
Authorities also said special crash investigators studied the scene for clues and that there were no skid or brake marks. While that was curious, authorities said there is no reason to believe the crash was a deliberate act.
Jennifer and Sarah were a married couple who had adopted six children. Three of the children's bodies were recovered from the scene.
The sheriff's office, the California Highway Patrol and the United States Coast Guard out of Fort Bragg initiated a second search after learning that three other children were missing following the crash.
Those three missing children were identified as 15-year-old Devonte Hart, 16-year-old Hannah Hart and 12-year-old Sierra Hart.
Devonte drew wide media attention after being photographed hugging a Portland police sergeant during a demonstration over the unrest in Ferguson, Missouri.
Clark County sheriff's Sgt. Brent Waddell told the Associated Press that the family lived in Woodland, Washington, and recently had a visit from Child Protective Services. He said the sheriff's office later entered the house and found no obvious signs of trouble or violence.
A couple who lived next door the family in Washington said they called police because they were concerned one of the children, Devonte, was going hungry.
Bruce and Dana DeKalb said they called CPS Friday after Devonte had come over to their home too often within the week to ask for food.
The DeKalbs recounted a night three months after the family moved in when one of the girls rang their doorbell at 1:30 a.m.
Bruce DeKalb says she "was at our door in a blanket saying we needed to protect her. She said that they were abusing her."
Online court records showed that Sarah Hart pleaded guilty to a domestic assault charge in Minnesota in 2011. There was also a dismissal of a charge of malicious punishment of a child. But no other details on the case were immediately available.
Authorities said the family appeared to be on a short road trip because many belongings remained in the home along with chickens and a pet.
The Associated Press contributed to this report.