Sen.: Up to 6,600 Mismarked Graves at Arlington

(CBS/ AP)  Updated at 5:33 p.m. ET

Estimates of the number of graves potentially affected by mix-ups at Arlington National Cemetery grew to as many as 6,600 on Thursday, as the cemetery's former superintendent blamed his staff and a lack of resources for the scandal that forced his ouster.

John Metzler, who spent the past 19 years overseeing Arlington National Cemetery, said the buck stops with him, reports CBS News chief White House correspondent Chip Reid.

"Personally it is very painful for me that our team at Arlington did not perform all aspects of its mission to the high standard required," he told a Senate panel. He was subpoenaed to testify.

But he blamed limited resources and said he only discovered the problem recently, infuriating Senator Claire McCaskill (D-Mo.).

"The notion that you would come in here and act like you didn't know about it until a month ago is offensive," she said. "You did know about it and you did nothing."

Metzler and his deputy, Thurman Higginbotham, were forced to retire after Army investigators found that as many as 211 graves were unmarked or misidentified.

McCaskill, chairwoman of an oversight panel on the Senate Homeland Security and Government Reform Committee, said Thursday that her investigation has revealed far higher estimates of the number of graves affected. She said she thinks that between 4,900 and 6,600 graves may be unmarked or mislabeled on cemetery maps. And she blamed Metzler.

He provided an often confusing defense, saying that internal working maps used by cemetery employees were mislabeled but that those discrepancies wouldn't necessarily affect operations.

He also said any problems that popped up over the years were quickly fixed and suggested he was surprised by the findings of the Army's Inspector General.

His testimony angered lawmakers.

"This is not complicated. It's called keeping track of who you bury where," McCaskill said.

A visibly frustrated Sen. Scott Brown (R-Mass.) abruptly ended his questioning.

"I'd have a lot of fun with you in a deposition because I don't think we're getting straight talk here," said Brown.

Higginbotham testified in general about his tenure at the cemetery but left the hearing early after asserting his Fifth Amendment right not to respond to many of the lawmakers' more pointed questions.

When asked whether he was aware of problems at the cemetery, Higginbotham said: "It was always conceptual that anything done by hand for 40-plus years that there would have to be some errors somewhere."

Arlington National Cemetery says anyone concerned about their loved ones can go to the cemetery's website for information or they can call 703-607-8199 Monday through Friday from 8 a.m. to 5 p.m. ET.