Image copyright Tristan Fortsch / KATU News Image caption Jennifer and Sarah Hart and their six children at a Bernie Sanders rally in Vancouver, Washington in 2016

An entire family has died after their vehicle plunged over a cliff in northern California, authorities say.

The bodies of Jennifer and Sarah Hart and three of their adopted teenagers were recovered after a passer-by saw their overturned SUV on Monday.

Investigators are still searching for three more children.

One of those missing, 15-year-old Devonte Hart, made headlines in 2014 after a photo of him crying and hugging a police officer went viral.

The image was taken at a protest sparked by the fatal shooting of unarmed black teenager Michael Brown by a white police officer in Ferguson, Missouri.

Authorities believe that Devonte and two other children were also in the car at the time of the incident.

Image copyright PA Image caption Devonte Hart, 15, is thought to have died in the crash that killed his family

"We know that an entire family vanished and perished during this tragedy," Mendocino County Sheriff Tom Allman was quoted by the Associated Press (AP) as saying.

Unanswered questions

The family, who lived in Woodland, Washington, was recently visited by Child Protective Services, a spokeswoman for the state's Department of Social and Health Services told AP.

The family is believed to have left their home for a short trip, but neighbours say they disappeared after Child Protective Services came to their home, according to CBS News.

Neighbours Bruce and Dana Dekalb reported the family to authorities on Friday and noticed their car was gone on Saturday morning.

"They portrayed this happy little family," Ms Dekalb told CBS News, "yet their daughter is telling us please, please, please, begging us not to go back they're abusing her".

They also claimed Devonte said he was being starved to death and asked them to leave food by the fence.

"He was asking that we not tell his mom, to hide it and put it by the fence so he could get to it," Mrs DeKalb told local television outlet KOIN.

Image copyright California Highway Patrol Image caption The car carrying the family landed in the Pacific Ocean

Sarah Hart was convicted in 2011 of domestic assault after one of the children had bruises on her arm that were noticed at school, according to local media.

Hart pleaded guilty and admitted to spanking her adopted daughter.

Mendocino County Sheriff Tom Allman said on Wednesday that the scene was unusual because the vehicle had travelled across 23m (75-foot) area separating the road from the cliff edge before the 31m plunge. No skid or brake marks were found at the scene.

But he added that there was "no evidence and no reason to believe this was an intentional act" and appealed for anyone with knowledge of the family's whereabouts before Monday to come forward.