Investigators revealed that two South Dakota girls who went missing in May 1971 died in a car accident, bringing closure to a cold case that has remained a mystery for over 40 years.

The announcement was made at a Tuesday press conference held by state and local authorities in Elk Point, the Associated Press reported.

The girls, 17-year-olds Cheryl Miller and Pamella Jackson, were on their way to a party to celebrate the end of the school year when their car drove off a gravel road and into a creek. The car and their bodies remained at the bottom of the creek, until a drought in the fall of 2013 exposed the car.

An investigation into Miller's and Jackson's disappearance found that the girls had not been drinking. An inspection of the car also found that it was in high gear, ruling out foul play, the AP reported.

"It's consistent with a car accident," Attorney General Marty Jackley said, the AP reported.

The cold case was thought to have been solved back in 2004, when David Lykken, who attended Vermillion High School with the girls, was suspected of being involved in their disappearance.

A search of the farm Lykken lived on turned up bones, a purse and photographs, the AP reported. However their car, a Studebaker, was not found.

Lykken was charged with two counts of murder in their disappearance. Those charges were later dropped when prosecutors found out an informant lied about Lykken confessing to murdering Miller and Jackson.

Lykken was convicted and sentenced on unrelated charges of rape and kidnapping, while Miller and Jackson's disappearance remained unsolved.  

The Studebaker was found when a fisherman told authorities he saw a wheel sticking out of the creek's water. Miller and Jackson's remains are to be returned to their families to be buried.

One official said he is not sorry for how the investigation was conducted, even after someone was wrongfully accused for girls' deaths.

"It's easy to second-guess what could have been done or should have been done," Union County Sheriff Dan Limoges said, the AP reported.

"It just wasn't meant to be until recently."