CONCORD, N.H. — The two steel drums, found 15 years apart, held two bodies each. Three of them girls under 10. All were partially dismembered.

Decades after they were dumped in the New Hampshire woods, investigators have no idea who they are.

Cold-case investigators almost always grapple with not knowing the name of the killer they’re seeking. But for the bodies of a woman and three girls found on the site of a now-defunct trailer park, investigators don’t know the victims’ names, either.

“The starting point in almost any homicide investigation is who the victim is,” said Senior Assistant Attorney General Jeffery Strelzin, who heads New Hampshire’s cold-case squad. “The most fundamental information is denied us.”

The first two bodies — a woman and a girl believed to be between 8 and 10 — were found by a hunter on the property of an Allenstown trailer park. The second set of bodies — a girl between ages 1 and 3 and another between 4 and 8 — was found in the same area 15 years later by an investigator who revisited the scene.

Of the 126 victims listed as missing or murdered on the cold-case squad’s website, only six — including these four — are unidentified.

Strelzin said New Hampshire investigators are partnering with scientists and investigators at the National Center for Missing and Exploited Children to take a fresh look at the case.

They are using digital technology to do more accurate facial reconstructions and using forensic tests to determine any biological relationships between the four victims. Investigators have said the woman and the two younger girls are biologically related.

“We’re concerned we’re not portraying that accurately,” Strelzin said. “We’re trying to update it with the best technology we have.”

Every cold case is a mystery, but Strelzin said the number of unidentified victims — including the three children — makes this one unique.

“There’s a killer out there walking around who did something this horrific,” Strelzin said.

Allenstown was a different kind of town back in 1985, police Chief Shawn Mulholland said.

“We used to have a lot of transient neighborhoods — very low-income mobile home parks — that we don’t have anymore,” he said, noting the town’s population has dropped by 700 to about 4,300 today. “Our crime rate used to be very high. It’s gone down considerably.”

When the bodies were discovered, investigators checked with elementary schools across the state to see if any children had failed to return to school. They reviewed records of who had camped in nearby Bear Brook State Park in the previous years and studied missing-person reports nationwide.

Investigators believe the four were killed sometime between 1977 and 1985. They are not saying how they were killed.

Strelzin said it seems staggering to many that four people could go missing and go unnoticed. “But they were discovered in 1985, and could have gone missing before,” he stressed. “There was no Internet. No smartphones. No 24-hour news like you have now.

“Put yourself back in time and you can easily imagine it,” he said.

Bob Lowery, head of the national center’s missing-children division, said the three are among about 3,500 children missing long-term that the center is investigating.

“This one’s going to be tough, but we’ll never give up hope and never stop trying,” Lowery said. “Someone’s got to be looking for them. We work with families who, for 50 or 60 years, are still looking for children.”