A skull found along a highway in California’s Sierra Nevada mountains decades ago has been identified as that of a woman who went missing in 1970, police said Wednesday.

The DNA match solved the mystery of whether Donna Lass was alive or dead but not what happened to her, and officials continued to ask for any information in the case.

The skull was found by a sheriff’s deputy in 1986 along Highway 20 and Interstate 80 — some 45 miles northwest of South Lake Tahoe — the Placer County Sheriff’s Office said. It was preserved at the coroner’s office as an unidentified person.

Lass was reported missing to the South Lake Tahoe Police Department in 1970, and the investigation exhausted all leads, officials said.

She was 25 years old, had just rented an apartment in South Lake Tahoe and was a nurse at a casino in nearby Stateline, Nevada, when she vanished, according to a news article from the period shared by the sheriff’s office. Left behind were her car, clothes and a bank account.

The DNA match was done through a cold case team which was recently formed in Placer County, the sheriff’s office said.

The skull was sent to the California Department of Justice, which was able to match the DNA to a sample given by Lass’ sister five years ago, South Lake Tahoe Police Chief David Stevenson told NBC affiliate KCRA of Sacramento on Wednesday. The match was discovered two weeks ago, police said.

South Tahoe Lake police said they have been in contact with members of the Lass family.

“We hope this development leads to closure after many years of searching,” the police department said in a statement.

A cryptic postcard sent to the San Francisco Chronicle in 1971 had a symbol resembling that of the Zodiac Killer and the words “Sierra Club,” “Sought victim 12,” “peek through the pines,” and the upside-down phrase “around in the snow,” the Sacramento Bee, which ran the postcard in a 1971 article, reported Wednesday.

That led to speculation that the disappearance could be linked to the still-unsolved serial killer case, but authorities have not connected Lass’ disappearance with the Zodiac Killer, the Bee reported.

In 2007, while acting on a tip related to the Zodiac killings, South Lake Tahoe police and others dug near Lake Tahoe looking for a possible burial site but found nothing, KCRA reported in 2013.

It remains unclear what happened to Lass.

“It hasn’t been proven to be a homicide at this point, but we’re obviously treating it that way,” Stevenson, the South Lake Tahoe police chief, told the station.

Anyone with information was asked to contact South Lake Tahoe police detectives at crimetips@cityofslt.us and reference case 0070-6436.