Detectives finally discovered the fate of the family who vanished in their car almost 70 years ago on their way to find Christmas decorations in Oregon.

The group of five went missing in December 1958 in a case that gripped America.

Two of the children were found dead months after the disappearance, but the other members had not turned up.

But now, parents Kenneth and Barbara, and daughter, Barbie Martin, have been identified from human remains found in the Columbia River, officials said.

The Hood River County Sheriff's Office finally concluded its decades-long investigation and, despite speculation, 'found no evidence of a crime.'

'The Martin family originally disappeared in December of 1958 while reportedly visiting the Columbia River Gorge to collect Christmas greenery,' the force said on social media on Thursday.

'The remains of Virginia and Susan Martin were found downstream months later, but the parents, Kenneth and Barbara, and oldest daughter Barbara (Barbie) were never found despite extensive searching and diving.'

Oregon State Medical Examiner's Office used DNA extracts from the remains and a profile of the Martin family's relatives to confirm their identity.

'This identification reflects a sustained coordinated effort, scientific partnership, and continued advancements in forensic genetic genealogy,' read the Oregon State Medical Examiner's statement.

The medical examiner's office had the help of the forensic genetics lab Ortham Inc, which specializes in processing evidence from cold cases.

The company's Chief Development Officer, Kristen Mittelman, told KATU this was a years-long process.

'So many people worked for years to find and identify the Martin family and we are proud to have helped,' she said.

'A mystery like this doesn't just weigh on the family, it weighs on the entire community and hopefully this gives a lot of people the resolution they deserve.'

It is a bittersweet ending to a cold case that had gripped the nation for the better part of 60 years.

The Martins were reported missing on December 9, 1958, after the parents failed to show up for work.

Upon initial investigations, authorities believed their car had accidentally backed into the Columbia River.

Barbara, Virginia and Susan were just 14, 13 and 11, respectively.

But many, including the family's eldest son, Donald, who was not in the car that day, suspect foul play.

The then-28-year-old, who was living in New York at the time, told detectives that he could not see how his parents' and sisters' deaths were an accident.

Detectives even offered a $1,000 reward for those who could offer information, reported WMUR.

A month after their disappearance, a gun was found near where the Martins vanished.

The sheriff's office did not collect it as evidence, but decades later, the gun owner's widow told local news that it had dried blood on it, the Daily Mail previously reported.

An autopsy report in 1959 cited a potential gunshot wound to the head for at least one of the daughters. The Medical Examiner had disputed the wound as a result of decomposition.

No suspects were ever named in the case.

But diver Mayo, who spent years searching for the family in the Columbia River, believed their disappearance was simply the result of a tragic accident.

'I think that they turned around in such a way that they kind of got stuck against a curb, put the car in reverse, and it wouldn't move, it wouldn't move, it wouldn't move,' he told KATU.

'And then all of a sudden jolted and it went backwards in an uncontrollable way into the water, and that's what they all do.'

'So, yeah, I have a theory,' he added. 'I mean, no one's ever going to know if it's right or not.'

The Daily Mail contacted the Hood River County Police Department and the Oregon State Medical Examiner's office for comment.