As many 6,600 graves at Arlington National Cemetery may be "unmarked, improperly marked or mislabeled" on cemetery maps, Sen. Claire McCaskill, D-Missouri, said Thursday.
Cemetery officials had previously estimated just 211 were mislabeled.
A Senate subcommittee is holding a hearing to examine the mismanagement of Arlington Cemetery, one of the nation's most hallowed burial places for its war dead.
The hearing was spurred by Army Secretary John McHugh's reports in June that revealed 211 graves were misidentified or mislocated in the historic cemetery.
A months-long investigation found "a lack of expertise in contracting processes within the cemetery, coupled with a lack of focused external oversight."
The probe exposed a dysfunctional management team with no oversight, missing documents, poor record keeping and failure to notify next-of-kin about the problems, according to the Inspector General's report.
McHugh said that "by placing everyone in charge, no one was in charge," and vowed to do "everything necessary and possible to right these unimaginable, unacceptable wrongs."
However, the cleanup launched in June did not include clearing out personnel.
After the investigation, the cemetery's former superintendent, John Metzler, who was scheduled to retire next month, was reprimanded. Metzler's former deputy superintendent, Thurman Higginbotham, was placed on administrative leave pending further review. The pair are invited witnesses at the hearing.
Army Inspector-General Steven Whitcomb said his review found no evidence of deliberate wrongdoing.
But Gina Gray, an Iraq veteran who is suing on grounds that she was fired for bringing the problems to light, wants to see someone held accountable for the blunders. She alleges the cemetery used outdated technology despite receiving millions of dollars to update its record-keeping systems.
"I don't know what it is going to take to get them fired over there," Gray said. "We have evidence of unmarked, mismarked graves, mismanagement going decades back."
McHugh said in June that a number of solutions are currently being considered for correctly identifying the remains in question, including exhuming graves for family members to identify their loved ones by the unique caskets containing them, opening the caskets to pick through articles and mementos, or, as a last resort, conducting DNA tests.
McHugh, sworn in as Army secretary in September, said the circumstances were allowed to continue due in part to fuzzy lines of oversight.
"I've restructured the administrative processes, and the lines of authority are pretty clear through the executive director, right down to my desk," McHugh said.
He said the solutions include pumping money into modern computer technology.
McHugh created a position to oversee operations at Arlington, and will personally supervise the superintendent position, he said.