Officials also are investigating claims that VA employees have falsified appointment records to cover up delays in care. An initial review of 17 people who died while awaiting appointments in Phoenix found that none of their deaths appeared to have been caused by delays in treatment.
"You've got an entrenched bureaucracy that exists out there that is not held accountable, that is shooting for goals, goals that are not helping the veterans," said Republican Rep. Jeff Miller, chairman of the House panel
"I think some people may by cooking the books" to suggest waiting times are shorter that they actually are, said Sen. Bernie Sanders, a Vermont independent who chairs the counterpart Senate committee.
Both chairmen were interviewed on CNN's "State of the Union."
President Barack Obama did not mention the VA issue in a speech on Sunday to U.S. troops in Afghanistan during a surprise visit.
"The VA really didn't factor into the planning for the trip at all," said Ben Rhodes, the deputy national security adviser. "The VA is obviously something he's going to continue to work on very hard in the coming days and weeks back home as well."
Meanwhile, Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, in a pre-recorded interview broadcast Sunday on ABC's "This Week," called the VA's current problems "outrageous — if the allegations are documented and proven. And I suspect some of them will be."
"They've got to be held accountable," Dempsey said, adding that Shinseki "has made it very clear that they will be held accountable,"
Meanwhile, Democratic Sen. Richard Blumenthal said on CBS' "Face the Nation" that the Justice Department "has to be involved." He said there is "credible and specific evidence of criminal wrongdoing across the country" at VA hospitals.
"We're not rushing to judgment. But the Department of Justice can convene a grand jury, if necessary," Blumenthal said.
The allegations have raised fresh concerns about the Obama administration's management of a department that has been struggling to keep up with the influx of veterans returning home from the wars in Iraq and Afghanistan, and Vietnam veterans needing more care as they age.
"You know, if we are going to send people off to war, we have a solemn promise to make sure that when they come home, we are going to take care of them," Sanders said.
The two committee chairmen appeared a day after the Obama administration agreed to recommendations from lawmakers in both parties and said it would allow more veterans to get care at private hospitals to help ease pressure on backlogged VA hospitals dealing with patients from the wars on terrorism as well as treating old soldiers from prior conflicts including Afghanistan and Iraq.
The problem is not a lack of resources, said Miller. "If money was the issue, this problem would have been solved a long time ago. VA is not using the resources that they're provided appropriately."
The VA says it is taking some of the pressure off its hospital system by allowing more veterans to be treated at private hospitals.
The VA spent about $4.8 billion last year on medical care at non-VA hospitals and clinics, spokeswoman Victoria Dillon said. That amounts to about 10 percent of health care costs for the Veterans Health Administration, the agency's health care arm.
It was not clear how much the new initiative would cost, Dillon said.
Said Sanders: "I think it's unfair to blame Shinseki for all the problems. Can he do better? Yes."