Washington (CNN) -- A "suspect" discovery at Arlington National Cemetery has led to a criminal investigation into how eight sets of human remains ended up in a single grave at America's most famous military burial ground.
It is the first criminal investigation after a series of recent revelations of misplaced human remains at Arlington.
The cemetery was tipped off this fall about a possible problem involving urns found in a pile of dirt several years ago by a contractor working at the cemetery.
When Kathryn Condon, who oversees the cemetery, asked about the two urns the contractor saw, an employee let her know that someone should look at a particular gravesite marked "Unknown."
Condon, who is executive director of the Army Cemeteries Program, called the Army's Criminal Investigation Command to help investigate.
A short time later eight urns containing human remains were found in the "Unknown" grave. Cemetery records indicated only one set of remains should have been in the grave, according to Kaitlin Horst, a spokeswoman for Arlington National Cemetery.
That discovery is what the Army is looking at.
Asked why it is a criminal investigation, Horst said, "The errors in past lent themselves to human error, mistakes that could have been made. But the fact that there were eight urns in one gravesite is pretty suspect. It doesn't seem to a mistake."
Of the eight urns found in the grave, three have been positively identified. One set was determined "unidentifiable" and that urn was reinterred in the grave where it was found.
The three that were identified were each in urns that contained a crematory tag. The tag is a metal of ceramic disk with numbers and initials on it. Army investigators were able to enhance the numbers and letters on the tags, which Criminal Investigation Command spokesman Christopher Grey said were in a "very poor state."
That helped them trace the urns back to the crematoriums they came from. Those crematoriums then gave the Army information that allowed them to identify the person whose ashes were in the urns.
One of those three urns has now been reinterred at Arlington in the location where it was supposed to be buried. The cemetery is working with the families of the people whose remains are in the other two urns.
Arlington National Cemetery is not releasing the names of the people whose remains have been identified.
The other four sets of remains did not include crematory tags, but it may be impossible to use DNA testing to identify them, a scientist said.
"It's very likely that the DNA was destroyed in the cremation process," said Dr. Frederick Fochtman, director of the Wecht Institute of Forensic Science and Law at Duquense University in Pittsburgh. However, he said, "it's worth a chance" to see if residual DNA, perhaps from bone tissue, could be used to make an identification.
Grey said Army investigators are "chasing other leads and using basic police work" to find out whose remains are in the last four urns.
Neither the cemetery nor the Army command would say when the original "unknown" grave was dug or when the veterans who were identified were originally buried.
Both Grey and Horst said that this latest incident dates back to the previous administration of Arlington National Cemetery.
Longtime Superintendent John Metzler was reprimanded by the Army after a number of problems with mismarked graves were discovered. Metzler and his second-in-command, Thurman Higginbotham, were allowed to retire last summer after the secretary of the Army told Congress there may be more than 200 mismarked graves in Arlington.
Grey would not say if either man is being questioned in this case.
Sen. Claire McCaskill, D-Missouri, called this case the latest in a series of "management errors" that she describes as "heartbreaking incompetence."
She's already sponsored a bill that will allow for closer oversight of Arlington National Cemetery. She plans to call for a vote on the bill during this week's rare Saturday Senate session.
As for the two urns in the dirt that the contractor first saw five years ago, no one seems to know what became of them.