Investigators made a grim announcement Wednesday in the hunt for relatives after an SUV plummeted off a cliff in Northern California: six children were feared dead, along with two women.

Crews earlier said three children had died and three were missing. The SUV plunged 100 feet from an ocean overlook on the Pacific Coast Highway about 150 miles north of San Francisco on Monday.

It's unclear what caused the SUV to drop off the cliff.

Jennifer and Sarah Hart, both 39, were confirmed dead earlier Wednesday, along with their children Markis Hart, 19; Jeremiah Hart, 14; and Abigail Hart, 14.

Later, Mendocino County Sheriff Tom Allman told reporters that investigators believed the couple's three other children -- Hannah Hart, 16; Devonte Hart, 15; and Sierra Hart, 12 -- were inside the vehicle and also died. Only three of the children's bodies were found in the area so far, Allman said.

Devonte made news after he was photographed at a 2014 protest in Portland, Ore., following a grand jury's decison not to indict a police officer in the shooting of a black man in Ferguson, Missouri.

Devonte, who is black, was holding a sign that read, "Free Hugs," when a white officer asked him for one. The photo showed an emotional Devonte embracing the officer.

"We have every indication to believe that all six children were in [the SUV]," Allman said. "We know that an entire family vanished and perished during this tragedy."

The sheriff said that nothing at this point indicates that the crash was intentional however investigators on the scene didn't find any skid or brake marks in the road where the car went over.

Allman pleaded for the public's help in piecing together the family's whereabouts in the days before the crash. He added that a witness called 911 about the incident but it wasn't clear when the SUV actually plunged over the ledge.

Appearances at the home indicated that the Harts were on a short road trip, as they left behind several personal belongings as well as chickens and their pet, California investigators said.

California Highway Patrol previously said the family was from West Linn, Ore., but they recently lived in Woodland, Wash., Clark County sheriff's Sgt. Brent Waddell told The Associated Press.

Child welfare officials made a recent visit to the residence, Waddell said. However, when the sheriff's department later went to the home, they reportedly didn't see any signs indicating trouble or violence. Investigators did not elaborate on that.

Neighbors of the family told The Associated Press they called child welfare officials as recently as this past Friday, fearing that one of the children was going hungry. Over the past week, Bruce and Dana DeKalb said Devonte Hart had been coming to their house asking for food.

The neighbors also recounted a night three months after the family moved in when one of the girls rang their doorbell at 1:30 a.m. Bruce DeKalb said she "was at our door in a blanket saying we need to protect her. She said they were abusing her."

Online court records obtained by The Associated Press showed that Sarah Hart pleaded guilty in 2011 to a domestic assault charge in Minnesota. Following her plea, a charge for malicious punishment of a child reportedly was dismissed.

The Associated Press contributed to this report.