In a memo released on Tuesday, a Senate subcommittee disclosed that it has “obtained information suggesting that 4,900 to 6,600 graves may be unmarked, improperly marked, or mislabeled” on the maps at the historic Arlington National Cemetery. These problems, according to the memo, are “far more extensive than previously acknowledged.”

The Subcommittee on Contracting Oversight gave kudos to Salon.com for a series of articles about the cemetery’s mismanagement, and to whistleblowers whose concerns went largely ignored for years.

The waste and contract mismanagement at Arlington, the memo pointed out, started years ago:

More than ten years ago, the Army began the development of a new system to automate the management of burial operations at Arlington National Cemetery. Documents and information obtained by the Subcommittee show that a series of improper actions and errors have wasted millions of dollars and delayed implementation of a functioning system by years.

Despite spending between $5.5 million and $8 million to develop a better system, “Arlington National Cemetery still does not have a system that can accurately track graves and manage burial operations,” the memo reads.

There are 330,000 grave sites at the cemetery--a burial place of military veterans, Supreme Court justices, U.S. presidents, former slaves and Civil War soldiers. The cemetery is managed by the U.S. Army.

In a hearing last month, Army Secretary John McHugh testified that the Army officials overseeing the cemetery were ignorant of the problems, Salon noted.

According to The Washington Post, the Army has known about these problems for almost 20 years but has been unable to solve them. The Senate subcommittee also found that the Army—which had divided oversight of the cemetery among several Army organizations over the years—had failed to conduct “even the most basic oversight.”

The subcommittee has subpoenaed some cemetery officials, and they are scheduled to testify on Thursday.