The mix up over tombstone labeling at Arlington National Cemetery could be much worse than originally reported.

Democratic Sen. Claire McCaskill revealed Thursday that as many as 6,600 graves at the historic burial ground for fallen soldiers may be "unmarked, improperly marked, or mislabeled."

In June, Army Secretary John McHugh said only 211 graves were mishandled. He ordered a thorough review of the cemetary and its operations.

Click play for an updated report with CBN News' Charlene Israel.

The probe exposed lapses in management, eventually forcing the cemetery's supervisor John Metzler out of his job.

Metzler initially blamed a lack of resources, but accepted "full responsibility" for the errors at a press conference Thursday. He expressed his regrets to the families affected.

McHugh said a number of solutions are being considered on how to correctly identify the remains that were mixed up. They include exhuming graves for family members to identify by casket, opening the caskets to pick through articles and mementos, or as a last resort, conducting DNA tests.

Some 330,000 veterans and their family members are buried at Arlington National Cemetery.