New speedometer clue in family's mysterious cliff plunge

A tragedy which saw a family's SUV plunge off a cliff, killing two mothers and at least three of their six children, may have been an intentional act, according to the California Highway Patrol.

"We do have reason to believe... that the crash was intentional. This is all based on preliminary information," Greg Baarts, Acting Assistant Chief for CHP, Northern Division, said.

Baarts said the CHP's investigations were far from conclusive, but he revealed the speedometer of the family's SUV was "pinned" at 144km/h, US television station KGW8 reported.

A CHP spokesperson addressed media on Sunday night revealing the SUV's on-board computer shows that the vehicle stopped at the side of the highway and then accelerated for 20 metres before plunging off the cliff.

The CHP spokesperson described the car's movements as "pure acceleration all the way."

Jennifer and Sarah Hart, both 39, died when the vehicle plummeted from a 100-foot cliff along the Pacific Coastal Highway in California, US.

Their bodies were discovered at the crash site on March 26 alongside three of their children's bodies. The couple's three other children are missing and may have been swept out to sea, authorities have said.

Investigators with the California Highway Patrol work at the scene where a couple and several of their children in their SUV plunged off. Source: AP

Markis Hart, 19, Jeremiah Hart, 14, and Abigail Hart, 14, were all killed in the crash. Hannah Hart, 16, Devonte Hart, 15, and Sierra Hart, 12, are yet to be found.

According to court documents cited by Fox 12 Oregon, the CHP believes "a felony has been committed".

On March 28, Mendocino County Sheriff Tom Allman said it appeared there had been no attempt to stop the vehicle near the cliff edge.

“It was a very confusing scene because there were no skid marks, there were no brake marks," he said.

Members of the Hart family pictured at the annual celebration of “The Goonies” movie in Astoria. Source: AP

On Wednesday, Allman had said that it was unable at this moment to say what caused the incident.

"We have no reason to believe, we have no evidence, that this was an intentional act. Certainly people are wondering what caused this," he said.

Tracks lead away from the edge of the cliff. Source: AAP

"If this was an intentional act, I truly believe we are going to come to that conclusion."

The car's discovery came three days after neighbours called child welfare authorities to visit the Hart’s rural Washington state home to investigate possible abuse or neglect.

The family had been living in Oregon until last year when they moved to Woodland, Washington.

Next-door neighbours Bruce and Dana DeKalb said they called child services last Friday because Devonte, now 15, had been coming over to their house asking for food.

A helicopter scours the scene as investigators try and understand what happened to the three missing children. Source: AP

Dana DeKalb said Devonte told her that his parents were “punishing them by withholding food.” He came over almost every day for a week and asked her to leave food in a box by the fence for him, she said.

Ms DeKalb said a Child Protection Services worker visited but the Harts did not open the door and left just hours later, KGW8 reported.

"The next morning when we saw that the vehicle was gone, and then Sunday morning when it still wasn't there, we figured something was off," Mr DeKalb added.

"We figured that they saw the business card and loaded up the kids as quick as they could and took off."

In 2011, Sarah Hart pleaded guilty to a domestic assault charge in Minnesota. Her plea led to the dismissal of a charge of malicious punishment of a child, according to court records.

According to a criminal complaint, a 6-year-old girl told a teacher at her elementary school that she had “owies” on her tummy and back and said, “Mom hit me.” Sarah Hart told authorities “she let her anger get out of control” while spanking her daughter.

Max Ribner, who has known the family since 2012, said allegations from neighbors don’t square with what he knows about the Harts.

“They are beautiful examples of opening arms to strangers, helping youth, supporting racial equality,” Ribner, who lives in Portland, said. “They brought so much joy to the world. They represented a legacy of love.”