A lesbian couple thought to have deliberately driven off a cliff with their six children in the car fled their home on the day a case worker visited them over abuse claims.

Jennifer and Sarah Hart, both 39, and their six African-American adopted children seemingly committed suicide in Northern California in late March.

Now it has emerged that the authorities were beginning an investigation into the couple over allegations they starved and whipped their children.

Jennifer and Sarah Hart, 39, were not wearing seatbelts when they drove off a cliff. From left to right: Hannah, Abigail, Sierra, Jeremiah, Jennifer, Devonte, Markis and Sarah Hart

The children asked neighbors for food on numerous occasions and one even reportedly leaped out of a window to try to escape, the documents reveal

An intake report from Washington State's Department of Social and Health Services filed March 23 paints a picture of horrific abuse leading up to the family's annihilation.

Neighbors' reports state the parents starved their children as a punishment and whipped them with belts.

The children asked neighbors for food on numerous occasions and one even reportedly leaped out of a window to try to escape, the documents reveal.

Their car found by Investigators believe that Jennifer drove the car off the cliff intentionally as there were no skid marks and evidence shows the speedometer was 'pinned' at 90mph

At least four reports of suspected child abuse in the Hart family were made during the past seven years.

The case has raised questions about the ability of authorities to track known offenders as the Harts had moved between three states during that period.

Prior to the deadly crash, they were living in rural Woodland, Washington. Before that they had spent time in West Linn, Oregon, and Douglas County, Minnesota.

The area where the Harts' car was recovered at the bottom of a scenic beauty spot

Steve Frkovich, whose daughter Dana DeKalb, 58, lived next door to the family in Washington, reported the Harts on November 18.

A recording of his 911 call was released by Clark Regional Emergency Services Agency in Washington State.

He told the cops 16-year-old Hannah Hart had fled from her home at 2am and begged his daughter to hide her.

His daughter told the girl's parents what had happened and all the Hart children came over and said everything was okay, said Frkovich.

'There are some kids that I feel are being highly abused,' he told the dispatcher.

'They were all standing at attention, like they were all scared to death. I think something very serious is going on.'

On March 23, DeKalb notified the department that she believed the children were being abused, according to media interviews and state records.

Sarah Hart pleaded guilty in 2011 to a domestic assault charge in Minnesota over what she said was a spanking given to one of her children.

Records showed that the Hart children were removed from public school in Alexandria, Minnesota the day after she reached a probation agreement stemming from the child abuse case in April.

That came a week after Hart pleaded guilty to physically abusing one of her daughters, who was six at the time.

The kids were taken out of school and moved to Oregon, where they were privately educated from there on out, the Oregonian reported.

The family later moved to Woodland, Washington, where they were living at the time of their deaths.

Authorities have said that data from the vehicle's software suggested the crash was deliberate.

Investigators believe that Jennifer drove the car off the cliff intentionally as there were no skid marks and evidence shows the speedometer was 'pinned' at 90mph.

They said the SUV had stopped at a coastal highway overlook before speeding straight off the cliff and plummeting 100 feet into the rocky Pacific Ocean below.

It fell into rocks and was found partially submerged about 100 feet below the highway.

The California Highway Patrol released a photo of Jennifer Hart shopping at a grocery store just a day before the crash.

The family appear to have left their home in Woodland, Washington on March 23.

Surveillance footage shows Jennifer Hart (right) checking out of a grocery store in Fort Bragg, California just hours before she is believed to have driven off a cliff with her wife and their kids inside

CHP believes the family then drove south on Highway 101, and then State Route 1, arriving in the Fort Bragg, California area 12 hours later.

It is believed that the family stayed the night in the area, since Jennifer was seen checking out of a Fort Bragg grocery store around 8.15am on Sunday, March 25.

Authorities say the family stayed in Fort Bragg until 9pm that evening, at which point it seems they turned around and started traveling north again on State Route 1.

Police searched the family's home about 500 miles north of the crash site but found no suicide note.

The Hart family gained attention in 2014 after one of the children was photographed crying in the arms of a white police officer at a protest after the fatal police shooting of an unarmed black teenager in Ferguson, Missouri.

Investigators are now examining 'red flags' in the Washington family's past in the hope of explaining why they drove off the cliff in an apparent suicide plunge.