Composite sketches from forensic artists at the National Center for Missing and Exploited Childrenof two of the four victims in the Bear Brook cold case. (Courtesy NCMEC)

One November morning in 1985, hunters came upon the 55-gallon drum in the New Hampshire woods. They opened it, and made a horrifying discovery. Stuffed inside were the bodies of a woman and a young girl.

Fifteen years later, investigators combing the woods for clues on the long-unsolved case came upon the unthinkable, just a short distance away: yet another barrel. This one contained the bodies of two more little girls.

For 15 years more, the trail led nowhere beyond those woods outside Allenstown, N.H. (pop. 4,322). DNA early on established the woman and two of the girls were closely related, perhaps mother and daughters, or siblings. But now advanced new technology has authorities making a push to solve one of the most baffling and gruesome cold cases in U.S. history.

Sketches have been released, and a newfound call for information has authorities hoping they can finally put names to the faces, and finally solve the Bear Brook Murders.

“We’ve actually never seen four unidentified bodies found together that remain unidentified after all these years,” said Carol Schweitzer, a senior forensic case specialist with the National Center for Missing and Exploited Children.

The latest forensic break is from the microscopic chemical clues in the victim’s bodies. Chemical isotopes in the four females’ hair, teeth and bones has narrowed down that they were from the northeast – and lived together for the weeks and perhaps months leading up to their deaths.

Watch the video of the Bear Brook murder investigation by the NCMEC.

Five elements in the remains of the four provided geographical clues, according to an analysis by George Kamenov, an associate researcher in geochemistry at the University of Florida.

Lead is simply an indicator of a large region – in this case indicating they were from North America and not Europe, Kamenov told Forensic Magazine in an exclusive interview. Strontium, carbon, and nitrogen are other elements that narrow down what the family was eating and drinking.

But oxygen, and particularly oxygen-18 and oxygen-16, are an even better indicator, since water has a signature in different regions.

Composite sketches from forensic artists at the National Center for Missing and Exploited Childrenof two of the four victims in the Bear Brook cold case. (Courtesy NCMEC)“Oxygen is the most useful in this case, since it reflects the water they were drinking,” Kamenov told Forensic.

The three females who were related could be narrowed down to two swaths on the map, one covering the Northeast including New Hampshire, the other extending from the North Central part of the U.S. southwest. However, the fourth female who is not related by blood lived in one of a handful of isolated areas in the Northeast, nearing the Canadian border, according to NCMEC.

“She came from a different place,” Kamenov said, in the phone interview.

DNA and other aspects of the remains have narrowed down the relations, too: the woman likely had dark, wavy hair and was between 22 and 33 years old. The oldest girl in the same barrel was 10 years old at the time of death. The youngest victim, who was also related, was 2 or 3 years old and had a large gap in the front of her teeth. The unrelated middle child was 3 or 4 years old and had a different appearance, according to the latest sketch.

All four victims lived in New Hampshire together prior to their deaths, they added. According to online sources, they could have been killed as early as 1977.

"For some reason, all four came together shortly before their deaths," Schweitzer added, in a phone interview today with Forensic.

But authorities are still hopeful.

“How could an entire family disappear and it take over 30 years to come to an answer as to who they are?” said Lt. Joseph Ebert of the New Hampshire State Police, in a video produced by NCMEC.

The isotope signature analysis was also used in the infamous “Baby Doe” case earlier this year in Massachusetts. The technique helped narrow down the geographical region, which was further focused by pollen traces on the clothing of the little girl, who was later identified. The mother was subsequently arrested.

The New Hampshire case is currently active and the New Hampshire State Police and NCMEC are seeking leads into the identity of the family.

"We have come so far in the last few years - even in the last few weeks. I'm hopeful," said Schweitzer. "It takes time to find the one person to put these pieces together."

Anyone with information is encouraged to call 1(800) THE-LOST.