The SUV appears to have stopped at a dirt pull-off area about 70 feet (21 meters) from the cliff at the edge of California's coastal Highway 1 in Mendocino County, about 180 miles (290 km) north of San Francisco, according to the vehicle's on-board computer.
Their three other adopted children were believed to be in the vehicle, according to deputies, but they have not been located.
The Mendocino County Sheriff's Office said the family may not have meant to stay away from home for long that day because many of their belongings, including a pet and some chickens, were still at their home.
A truck drives by the pullout where the SUV of Jennifer and Sarah Hart was recovered off the Pacific Coast Highway, near Westport, California on March 28.
A family's SUV plunged off of a California cliff on Sunday afternoon.
The family had previously lived in a suburb of Portland, Oregon, before they moved north across the Columbia River to Woodland, Washington.
The CHIP said electronic data pulled from SUV has helped them piece together the family's final tragic moments.
He told NBC News that California authorities are "tirelessly searching for the missing children along the coastline", while authorities in both California and Washington are "conducting interviews and attempting to establish a timeline and routes of travel in an effort to rule out any other possibilities".
Nov, 15, 2010: One of the Hart's daughters Abigail, then 6 years old, told her teacher that she had "owies" on her tummy and back, according to a complaint filed in Minnesota. The boy asked her to leave food in a box by the fence for him, she said.
Devonte, a young black boy, was photographed in 2014 crying in the arms of a white police officer during a protest in OR over police brutality in Ferguson, Missouri.
DeKalb said that he had called Child Protective Services March 23 and they had arrived at the house just after Jennifer Hart came home from work but that she didn't answer the door.
The DeKalbs also said one of the daughters showed up at their doorstep in the middle of the night, covered in blackberries because she had walked through blackberry bushes trying to escape her home.
"The most-likely cause for that reading is the shock from the impact", Baarts said. Child welfare authorities failed to contact the family on two subsequent visits in March. When investigators searched the Harts' most recent home, in Woodland, Wash., they found family belongings, pets and some chickens, but not the three missing children.
The agency had no prior history with the family, said Norah West, a spokeswoman with the Department of Social and Health Services. According to court documents, the girl later told a detective and social worker that her mother hit her, leaving bruises.
Investigators were looking at a "variety of felony crimes to investigate this with", Baarts said.
Since the accident, information has emerged that Jennifer and Sarah Hart, both 39, had been investigated over the treatment of their children.
Neighbors Dana and Bruce DeKalb told the Oregonian newspaper that Devonte had asked them for food for himself and his siblings after his parents withheld it as punishment.
KPTV reported that investigators have secured a warrant to search the family's home, including documents such as bank and cellphone records, credit-card statements, journals and suicide notes.
Nevertheless, without elaborating, he added, "There have been red flags".