Updated November 8, 2021 at 5:17 PM ET

A nearly 40-year-old case of a missing Massachusetts teen who vanished after a party may have been solved thanks to a recent grim discovery brought on by new sonar technology.

Massachusetts state investigators say portions of a 1972 Dodge Dart Swinger that belonged to 17-year-old Judy Chartier, a girl who went missing from a party in 1982, were found in the Concord River in Billerica on Wednesday.

The following day, authorities say divers who were searching the area also discovered human remains; the remains were positively identified through dental records by authorities as Judy Chartier's.

"Sadly, this discovery comes after nearly 40 heartbreaking years of Judith's friends and family missing her and wondering about what happened that day," said Middlesex County District Attorney Marian Ryan said in a news conference.

Ryan says authorities are still processing Judy's car for additional evidence, emphasizing that county and state officials will continue the search for answers in the years-long cold case.

"First to hear just a little bit of news, that we've been able to locate the car, and then to hear ... that we've actually found human remains, is both heartening in that [the family] will now have a sense of what happened to their sister, but also very distressing in terms of all the years they have waited," she said.

Investigators say the area where Judy's car was found looks different now than what it did four decades ago, leaving them with the task of reconstructing the physical area in addition to the circumstances under which she went missing.

Ryan says it's too early in the investigation to tell whether foul play is suspected

On June 5, 1982, 17-year-old Judy went missing after leaving a party in Billerica, about 25 miles north of Boston.

Friends reported that she was last seen around 2 a.m. on the night of the party, state authorities say. This was the last known sighting of her.

The next morning, Judy's brother, Joe, said two men who were acquaintances of Judy's fiancé told the Chartiers that she was missing, according to the Boston Herald.

Since her disappearance nearly 40 years ago, the only surviving members of the Chartier family are Joe and another sibling, the Herald reports. Her parents and other siblings have since died.

"Their parents are no longer with us and obviously went to their grave not knowing what happened to their daughter," Ryan said.

During the news conference, Ryan told reporters it's too early in the investigation to tell whether foul play is suspected, adding that a second opinion from a medical examiner and a forensic anthropologist will determine it.

Chelmsford, Mass. Police Chief James Spinney says the dive team will soon return to the waters to uncover more evidence, in hopes of solving the case.

Copyright 2021 NPR. To see more, visit https://www.npr.org.