Police say they might never know what caused SUV carrying family of eight to plunge off California cliff, killing at least five passengers

Brake failure, a blown tire and factors such as the weather and road condition are among the factors that will be looked at by investigators trying to determine what caused an SUV carrying a Washington state family to plunge off a California cliff, but authorities might never figure out exactly what happened.

One of the children, Devonte Hart, drew national attention after the black youngster was photographed in tears, hugging a white police officer during a 2014 protest in Portland over the deadly police shooting of a black man in Ferguson, Missouri. Devonte was holding a “Free Hugs” sign.

Authorities don’t know exactly when or how the SUV – which was discovered Monday – went over the cliff alongside a spot commonly used by motorists to walk their pets. They say they have no reason so far to believe it was an intentional crash that claimed the lives of two women and at least three of their six adoptive children just days after child welfare authorities tried to contact the family over concerns about the kids’ living conditions.

But they also said there were no skid marks or signs the driver braked as the GMC Yukon crossed a flat dirt pull-off area, about 75ft wide, and went over the edge of the Pacific Coast Highway.

“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 appealed to anyone who might have seen the family of eight to come forward. Three other children are missing and presumed dead.

The wreck was discovered by a passing motorist on Monday afternoon. The women, both 38, were found dead inside the SUV, while three of their children – Markis Hart, 19, Jeremiah Hart, 14, and Abigail Hart, 14 – were discovered outside the vehicle.

A team on Thursday continued to search the rugged coastline for the three other children, also believed to have been in the SUV: Hannah Hart, 16, Sierra Hart, 12, and Devonte.

The brood was known as the Hart tribe, a multiracial family of two women and six children who grew their own food, took spontaneous road trips to camp and hike, and traveled to festivals and other events, offering free hugs and promoting unity.

Experts say accident reconstruction experts will have information to work with as they study how fast the car was going and other factors.

That model of Yukon was also 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.

Investigators can calculate the SUV’s speed based on where it landed and the height of the drop. “It’s basic physics,” Mazza said.

Family friend Max Ribner took issue with the notion it was something other than a tragic accident. The couple – Sarah and Jennifer Hart – adopted the six children, many of whom came from “hard backgrounds,” he said. “They transformed these kids’ lives.”

On Thursday, authorities in Washington state also searched the family’s home for information. The Clark county sheriff’s office said deputies were looking for bills, receipts or anything else to shed light on why the family left and other circumstances related to the trip, KGW-TV reported.

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 six-year-old adoptive daughter, court records show.

Then, last week, Bruce and Dana DeKalb, next-door neighbors of the Harts in Woodland, Washington, called state child protective services on Friday because Devonte, now 15, 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 “punishing them by withholding food”. The boy asked her to leave food in a box by the fence for him, she said.

Social service authorities opened an investigation, and a state caseworker went to the house last Friday 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.

By Saturday, the family’s SUV was gone from the driveway, said Bruce DeKalb.