SAN FRANCISCO (CBS SF/AP) — DNA test results have positively identified human remains found on a Mendocino County beach as one of six children from a family killed when their SUV plunged off a Highway 1 cliff in March 2018, authorities announced Wednesday.

The Mendocino County sheriff’s department said DNA testing by the California Department of Justice Bureau of Forensic Services Laboratory of a partial foot inside a shoe attached to a pair of jeans found on a beach below the cliff belonged to 16-year-old Hannah Hart.

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The sheriff’s department had trouble identifying the human remains found shortly after the March 26 crash until the biological mother of the 16-year-old called the department from Mobile, Alabama, in October. She was responding to a request from investigators for family members to come forward and help with the identification process.

The woman’s DNA sample matched the teen’s remains, the sheriff’s department said.

Hannah was one of six children killed when 38-year-old Jennifer Hart drove the SUV over a 100-foot cliff into the ocean. Investigators concluded that Hart was drunk and the crash was intentional.

Toxicology results showed that Hart’s wife, Sarah, and several of the children had large amounts of a drug that can cause drowsiness in their systems at the time of the crash.

Authorities said the vehicle’s software also revealed that 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.

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Investigators have never offered a motive for Jennifer Hart’s actions.

Authorities said the victims that have been positively identified are Jennifer Hart (38 years of age), Sarah Hart (38 years of age), Markis Hart (19 years of age), Hannah Hart (16 years of age), Jeremiah Hart (14 years of age) and Abigail Hart (14 years of age). Jennifer and Sarah Hart were married to each other.

Teenager Devonte Hart, who was believed to also be in the SUV, is still listed as a missing person.

The crash happened just days after authorities in Washington state, where the family moved in 2017 from Oregon, opened an investigation following allegations the children were being neglected.

A neighbor of the Harts in Woodland, Washington, had filed a complaint with the state, saying the children were apparently being deprived of food as punishment. No one answered when social workers checking on the report went to the family’s home near Portland, Oregon, on March 23.

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Three days later, their SUV was found partially submerged on the ocean, below a rugged cliff.