SAN FRANCISCO -- Accident-reconstruction investigators are trying to figure out what caused anto plunge off a 100-foot cliff in a deadly wreck that happened shortly after child-welfare authorities went to their home to investigate possible abuse. Five members of the Hart family -- a free-spirited brood from Washington state who grew their own food and took up activist causes -- were found dead, and the search continued Friday for three more children believed to have been in the vehicle when it went over the edge and landed on the rocks below the Pacific Coast Highway.
According to CBS News affiliate KOIN-TV, a search and rescue team of 9 people and a cadaver dog are searching the area where family was found dead.
"There are a lot of unknowns on this," Mendocino County Sheriff Tom Allman said. "Several of the questions that have been asked today will never be answered."
Allman said there is no reason so far to think the crash was intentional, but he also said there were no skid marks or signs the driver braked as the GMC Yukon crossed a flat, dirt pull-off area, about 75 feet wide, where motorists often walk their dogs.
Accident-reconstruction experts said investigators would look at road conditions along with such possibilities as brake failure or a blown tire. According to KOIN-TV, CHP officers say they are unaware of any mechanical problems with the SUV.
The sheriff appealed to anyone who might have seen the family of eight to come forward.
The brood was known as the Hart Tribe, a multiracial family of two women -- Sarah and Jennifer Hart -- and six adopted children who took spontaneous road trips to camp and hike and traveled to festivals and other events, offering free hugs and promoting unity.
One of the missing children, Devonte, drew national attention when the black youngster was photographed hugging a white police officer during a 2014 protest in Portland, Oregon, over the deadly police shooting of a black man in Ferguson, Missouri. Devonte was holding a "Free Hugs" sign.
The wreck was discovered by a passing motorist Monday afternoon, three days after social service authorities opened an investigation that was apparently prompted by a neighbor's complaint that the children were being deprived of food.
in Woodland, Washington, on March 23 but didn't find anyone home, state officials said. The agency had no prior history with the family, said Norah West, a spokeswoman with the Department of Social and Health Services.
Bruce and Dana DeKalb, next-door neighbors of the Harts, said they called state child protective services because 15-year-old Devonte had been coming over to their house almost every day for a week, asking for food.
Dana DeKalb said Devonte told her his parents were "." The boy asked her to leave food in a box by the fence for him, she said.
Authorities don't know exactly when the wreck took place. But by Saturday, the family's SUV was gone from the driveway, said Bruce DeKalb.
Well before the wreck, Sarah Hart pleaded guilty in 2011 to a domestic assault charge in Douglas County, Minnesota, telling authorities "she let her anger get out of control" while spanking her 6-year-old adoptive daughter, court records show.
The two women, both 38, were found dead inside the SUV, while three of their children -- Markis, 19, Jeremiah, 14, and Abigail, 14 -- were discovered outside the vehicle. The search continued for Hannah Hart, 16, Sierra Hart, 12, and Devonte.
That model of Yukon was presumably equipped with a black box recorder that would show its speed and use of the brakes, said Marcus Mazza, an engineer and accident-reconstruction expert with Lancaster, Pennsylvania-based Robson Forensic.
On Thursday, authorities in Washington state searched the family's home. The Clark County Sheriff's Office said deputies were looking for bills or anything else that could shed light on why the family left and other circumstances related to the trip.
Family friend Max Ribner took issue with the notion the wreck was something other than a tragic accident. The couple adopted many of their children from "hard backgrounds," he said. "They transformed these kids' lives."