WASHINGTON • Investigators believe that problems at Arlington National Cemetery may be more extensive than previously reported, with millions of dollars wasted on contracting and thousands of graves — rather than hundreds — unmarked, wrongly identified or mislabeled on maps.

Documents released Tuesday by the Senate Homeland Security Subcommittee on Contracting Oversight identified failures that include spending between $5.5 million and $8 million for a grave-tracking system that was never completed.

"Despite these expenditures, Arlington National Cemetery still does not have a system that can accurately track graves and manage burial operations," according to a memo from investigators based on interviews and a review of more than 5,000 pages of documents submitted by the Army.

The panel is looking into gross mismanagement disclosed last month at a cemetery that is hallowed ground to many Americans. The growing scandal will be the subject of a hearing Thursday conducted by Sen. Claire McCaskill, D-Mo., chairwoman of the contracting subcommittee.

A spokeswoman for McCaskill said Tuesday that subpoenas to testify have been issued for two former Army officials who were in charge of the cemetery.

The officials, John Metzler, the cemetery's former superintendent, and Thurman Higginbotham, who was his chief deputy, had declined an invitation to attend.

Among the documents released by the subcommittee was an Army investigative report noting "a poor working relationship" between Metzler and Higginbotham.

In June, the Army's inspector general released a report detailing major flaws at Arlington, where more than 330,000 people are buried.

The inspector general's report found mistakes associated with graves, including incorrect information about whether graves were occupied and mishandling of cremated remains.

The Army removed Metzler and Higginbotham after that report.

McCaskill's panel was established last year to ferret out contracting abuses. Investigators said that in the course of examining Arlington contracts, they obtained information suggesting problems with between 4,900 and 6,600 graves. The Army inspector general had found 211 errors in a survey of three sections of the cemetery.

Investigators said in a memo that they based their projections on the likelihood of a similar error rate throughout the cemetery's 70 sections. They noted that a contractor doing a survey six years ago in just two sections reported "many" locations where the cemetery records were inaccurate, among them a grave site reserved for a future occupant that had been occupied for years.

The subcommittee said that the Army insisted on a plan to create its own automated burial management system even though the Department of Veterans Affairs already had developed one of its own. The VA maintains burial records for more than 2 million individuals at 131 national cemeteries using a tracking system that cost about $2.4 million.

According to subcommittee investigators, the Army ended up with a computerized system that didn't work properly and then repeatedly tried to fix it despite warnings from the cemetery's information technology manager.

Citing the Army inspector general's report, investigators said that the cemetery failed to digitize more than 300,000 paper burial records. As part of that failed effort, a company operating under a no-bid contract was paid $800,000 for scanning files of burial documentation and delivering the results on CDs that were never used. Another contractor was paid $226,000 to validate records in two of the cemetery's 70 sections and convert the information into electronic form. But none of that work could be found.

Investigators asserted that Army officials "failed to conduct even the most basic oversight of the cemetery" and that Army contracting officials had paid little attention to the problems.

"When asked about their failure to look at Arlington National Cemetery, Army Contracting Command officials told subcommittee staff that, with more than 285,000 contract actions and $97 billion in contract spending ... small dollar values like the IT contracts at (the cemetery) were less likely to receive attention," investigators wrote.