(CNN) -- South Dakota investigators have put to rest a 42-year-old cold case about two missing 17-year-old girls, declaring they died in a car accident that ended in a creek at night in 1971, with no signs of foul play.
Cheryl Miller and Pamela Jackson were high school students when they disappeared May 29, 1971, while driving to a party at a gravel pit.
It took 42 years for their car to be discovered -- last September -- just a half-mile from the girls' intended destination near Beresford, South Dakota. Last year's weather -- a wet spring followed by strong creek currents and then a drought -- caused the car to become visible and recovered, caked in mud, authorities said.
Subsequent DNA, forensic and anthropological analyses confirmed the identities of the two sets of remains found in the car and also concluded that the girls' deaths were accidental, South Dakota Attorney General Marty Jackley told reporters Tuesday.
Their 1960 Studebaker Lark's ignition and headlights were turned on, and the transmission was in the top, or third, gear, Jackley said. Their clothing contained bones and remnants of shoes were found, and no evidence of alcohol was found in the car, he said.
"No evidence indicates that there was foul play. This would appear to indicate an accident," Jackley said.
The announcement "brings a closure" and gives the families "some answers," Jackley said. The families will now be able to collect the two girls' remains, he added.
The attorney general said investigators don't know what caused the accident, but he noted that one car tire was damaged, though authorities don't know whether a blowout caused that. He also cited how the tread on the tires were low.
Jackley showed reporters some of the personal belongings found in the car, including two classmate notes and Miller's purse.
Kay Brock, Jackson's sister, told CNN affiliate KSFY that the DNA confirmation finally ended the long uncertainty.
"I'm relieved to have no foul play," Brock told the station. "It's nice to have a permanent answer after 42 years."
CNN's Josh Levs contributed to this report.