WASHINGTON— As many as 6,600 graves at Arlington National Cemetery could be unmarked or mislabeled, thousands more than the initial estimates, a Senate panel learned Thursday.

The former superintendent said he didn’t know how the problem could have happened.

“As frustrated as you are with this, we are even more so,” John Metzler, the former superintendent at Arlington, said during during testimony at a Senate subcommittee looking into the issue.

Arlington Cemetery hearing

Photo by Chip Somodevilla/Getty Images

Thurman Higginbotham, right, former deputy superintendent of Arlington National Cemetery, listens to John Metzler, former superintendent at Arlington, testify to the Senate Homeland Security and Governmental Affairs Committee’s Contracting Oversight Subcommittee on Thursday at the Dirksen Senate Office in Washington. The subcommittee is investigating millions of dollars in botched information technology and record-keeping contracts overseen by the Army at the cemetery.

Sen. Claire McCaskill, D-Mo., who chairs the subcommittee, said Thursday her investigations have found that 4,900 to 6,600 graves are unmarked or improperly labeled, up substantially from the hundreds reported in the first estimates.

Metzler and Thurman Higginbotham, the former second-in-command at Arlington, repeatedly told senators that any issues stemmed from a lack of funding or mislabeled maps from years past. Close to $8 million was spent installing a new tracking system to replace handwritten note cards, but that new system still does not work, they said. Higginbotham, who oversaw that system, invoked his Fifth Amendment right not to testify and was eventually dismissed from the hearing.

“The top priority should be identifying the people who are national heroes for this country,” said Sen. Scott Brown, R-Mass. “The priority should’ve been given to the fallen that are buried there, not fax machines or copy machines. It’s 2010 and we’ve got all the technology and you’re still dealing with 3-by-5 cards. It’s a joke.”

McCaskill echoed Brown’s sentiments and said Metzler’s plan to create a new grave tracking system, instead of modifying a system used by the Department of Veteran Affairs in its cemeteries, showed a lack of management.

“We are here today because people had had enough and they blew the whistle,” McCaskill said. “This is not about lack of resources. This is not about that you have a complicated job. It’s called keeping track of who you bury where. That is not a complicated task. And the notion that you would come in here and say you didn’t know about it until a month ago is offensive. You did know about it and you did nothing.”

When pressed further by the senators to answer questions with clear responses, Metzler repeatedly said he was unaware of any problems, to which an exasperated Sen.Susan Collins, R-Maine, finally said, “Your answers make no sense to me whatsoever.”

The online magazine Salon first reported the problems at Arlington, home to more than 330,000 graves, in July of 2009. That prompted an Army investigation into the apparent mismanagement at the cemetery and caused both Metzler and Higginbotham to lose their jobs.