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Two men scavenging for scrap metal in an abandoned St. Louis apartment building 30 years ago came upon a ghastly discovery that would become one of the city's most haunting mysteries -- the headless body of a young girl, nude from the waist down.

The identity of the little "Jane Doe" was never determined. About all that forensic anthropologists could tell about her at the time was that she was African-American, somewhere between 8 and 11 years old, and tall for her age. No suspects were arrested and efforts to match her to missing children were futile. She was buried in an unmarked grave in a decrepit cemetery, as anonymous in death as she had been in life.

Three decades later, on a hot, sunny June morning, the child's remains were exhumed in hopes that modern forensic science can finally determine who the little girl was -- and who killed her with a brutality that shakes the human conscience.

"We never had a child killed like that," recalled Joe Burgoon, a 43-year veteran of the St. Louis Police Department who was among the first homicide detectives at the scene. "I thought about her every time I drove by that cemetery."

The remains taken Monday from the small wooden casket are now with the St. Louis medical examiner, who, with the help of forensic scientists, will try to extract new DNA and examine minerals in the bones that might pinpoint which part of the country the girl came from.

Investigators believe the child was not from Missouri, since no one in the state reported her missing, Burgoon said. And searches of schools in the area for students who had withdrawn or transferred yielded no one who matched the girl's description.

Two men searching for a pipe to fix their car found the body on Feb. 28, 1983, when they entered the basement of a boarded-up apartment complex at 5635 Clemens Avenue. When the two walked into a dark furnace room, a flicker from their cigarette lighter revealed the grisly sight. The headless child was lying on her stomach -- her hands bound behind her back and wearing only a bloodied yellow sweater with the tag removed. The men ran from the building and called police, who arrived within minutes.

"We saw she was just a little girl," said Burgoon, adding that police suspect she had been sexually assaulted before she was strangled and later decapitated with a long-bladed knife.

Burgoon and others believe she was killed elsewhere and later placed in the basement because there "wasn't much blood at the scene."

"Whoever carried her brushed against the wall and there were little streaks of blood," Burgoon said.

Without the girl's name, local police and investigators with the FBI's behavioral science unit were limited in creating a profile of the killer or killers.

X-rays taken at the time showed no sign of trauma, broken bones or scars that might have indicated previous abuse, according to Burgoon, who also noted that the sweater appeared to be newly purchased.

"He [the killer] had to be familiar with the area," he said. "It's possible she was killed by a relative or someone she knew because her head was taken off."

"But who knows what these killers think," Burgoon added. "Anything is possible. It could have been a stranger."

The latest effort to identify Jane Doe might never have been possible without the work of Abby Stylianou, a 23-year-old research associate in the Department of Computer Science & Engineering at Washington University.

The child's grave was not marked inside the poorly-run Washington Park Cemetery, so Stylianou and her team used old newspaper photos taken at the funeral 30 years ago and current aerial images from the U.S. Geological Survey to locate the exact burial spot. A group of local students raised money for a headstone last year, but had placed it at the wrong grave site, according to Stylianou.

"We were given access to eight photos taken on the day she was buried," she told FoxNews.com. "There were trees and headstones [in the photos] that we know haven't moved."

Stylianou and the other researchers found the grave just left of a tree that was not in the photos 30 years ago.

"This project was a very different application of our research, and it was tough," said Stylianou, adding that she had mixed emotions upon finding the casket.

"I felt an overwhelming sense of sadness about what got her to that point," she said. "But now there's hope we can figure out who she was."

And possibly seek justice.

"That is a great feeling," she said.

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