WASHINGTON -- Army officials today acknowledged finding more problems at Arlington National Cemetery and said a criminal investigation had begun into contracts for a failed computer system for grave-tracking.

During a contentious Senate Homeland Security subcommittee hearing, angry senators lectured Army officials and ex-employees of Arlington National Cemetery amid a growing scandal that the Army says could have criminal implicatios.

Sen. Claire McCaskill, D-Mo., who chairs the panel, called recent revelations "shocking "and told Army officials that they will be held accountable.

"Bodies accidentially buried in the same graves. Unmarked and mismarked graves. Urns of cremated remains being found in the cemetery's landfill. And the heartbreaking tragedy of the families who now can not trust the cemetery to tell them where their loved ones are buried," she said.

Sen. Scott Brown of Massachusetts, the panel's ranking Republican, said that the failures "have tarnished the sacred trust with military families ... and eroded the confidence of the families of our fallen heroes have that the remains of their loved ones will be respected."

The former cemetery superintendent and his assistant showed up at the hearing after being subpoenaed by the subcommittee. Both were forced to retired this month.

John Metzler, the former director, said he regretted any pain felt by families of people interred at Arlington.

But in testimony that often confounded the committee, Metzler asserted that he didn't know of problems until recently and asserted that he was well along to getting the computer system up and running when an investigation halted progress.

His testimony left senators shaking their heads.

"This is not complicated," McCaskill said. "It's called keeping track of who you buried where. The notion that you would come in here and act like you didn't know about it until a month ago is offensive."

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

Metzler's assistant, Thurman Higginbotham, refused to answer most questions, citing his 5th Amendment right to avoid incriminating himself. Higginbotham was in charge of the consultant contracts that failed to produce an automated tracking system for graves.

Before he was dismissed from the hearing, Higginbotham, who was acting superintendent when Metzler arrived, said he hadn't been permitted to apply for the full-time job. But he disputed Army reports that a poor working relationship with Metzler contributed to the problems.

The subcommittee is examining whether contracting failures contributed to the problem. Brown said that as much as $10 million was spent for a grave-tracking system that still doesn't work.

Brown held aloft an iPAD shaking his head. "We've got cell phones. We've got this and that and you guys are still using three-by-five cards."

The Army inspector general disclosed in a damning report last month that more than 200 graves were mismarked. But McCaskill said in her opening statement that the problems could be much more extensive and that between 4,900 and 6,600 graves may be unmarked, improperly marked or mislabeled on cemetery maps.

During questioning by senators, Kathryn Condon, the recently installed director of the Army cemeteries program, said that more "discrepancies" have been found since the inspector general report.

The inspector general had discovered more than 200 mismarked graves or other inaccuracies in surveying just three of the 70 burial sections at Arlington.

"I'm confident that there are probably other map errors," Condon said, referring to the locations of where people are buried.