FBI Director James Comey said Wednesday that the investigation was being led by the FBI's field office in Phoenix, which he described as the "primary locus of the original allegations" being investigated by the VA's Office of Inspector General.
"We're working with the VA IG to follow it wherever the facts take us," Comey told the House Judiciary Committee.
The inspector general said in a report last month that 1,700 veterans seeking treatment at the Phoenix VA hospital were at risk of being "forgotten or lost." The VA has confirmed that at least 35 veterans died while awaiting treatment in Phoenix, although officials say they do not know whether the deaths were related to long waiting times for appointments.
Comey did not elaborate on the investigation, but a Justice Department official said earlier Wednesday that the department had formally asked the FBI to investigate allegations related to the VA. The official spoke on condition of anonymity because the official was not authorized to discuss an ongoing criminal investigation on the record.
Comey's remarks came as the Senate was poised to vote as soon as Wednesday on a measure making it easier for veterans who have encountered delays getting initial visits to receive VA-paid treatment from local doctors instead. The measure closely resembles a bill approved unanimously Tuesday in the House, prompting optimism among lawmakers from both parties that a compromise version could be on its way soon to President Barack Obama for his signature.
"Maybe we can show the United States of America that people can come together on a very, very important issue and do it in rapid fashion," said Sen. Bernie Sanders, I-Vt., chairman of the Senate Veterans Affairs Committee.
The Justice Department had said that federal prosecutors were reviewing documents from the inspector general to determine whether to launch a full-fledged investigation. The involvement of the FBI represents an escalation into concerns of possible criminal conduct by VA employees, though it remains unclear whether investigators will find any basis for prosecution.
Richard Griffin, the VA's acting inspector general, issued a scathing report last month that confirmed allegations of excessive waiting time at VA hospitals and inappropriate scheduling practices. He told lawmakers his investigators were probing for wrongdoing at 69 agency medical facilities, up from 42 two weeks ago
The VA, which serves almost 9 million veterans, has been reeling from mounting evidence that workers falsified reports on wait times for medical appointments in an effort to mask frequent, long delays. An internal audit released this week showed that more than 57,000 new applicants for care have had to wait at least three months for initial appointments and an additional 64,000 newly enrolled vets who requested appointments never got them.
VA Secretary Eric Shinseki resigned May 30, but the situation remains a continuing embarrassment for Obama and a potential political liability for congressional Democrats seeking re-election in November.
Senate Democratic leader Harry Reid said Congress should act as soon as possible.
"It's urgent that we get this done to resolve some of the outstanding issues within the VA," he said.
Sen. John McCain, R-Ariz., a chief author of the Senate measure, said it shouldn't be hard for the two chambers to craft a compromise version. "I don't think there's a lot of major differences," he said.
Sanders, who co-wrote the Senate bill with McCain, said that by Senate standards, lawmakers were moving at "lightning speed."
The House and Senate bills each would spend hundreds of millions of dollars to hire more doctors and nurses, but that may be easier said than done, given a nationwide shortage of primary care physicians.
Primary care physicians are expected to become increasingly in demand as millions of people newly insured under the federal health care law start looking for regular doctors. The Association of American Medical Colleges has projected that by 2020, there will be 45,000 too few primary care physicians, as well as a shortage of 46,000 surgeons and specialists.
Shortages tend to be worse in both rural and inner-city areas.
The American Medical Association added its voice as the House was voting Tuesday. At its annual policy meeting in Chicago, the AMA approved a resolution urging Obama to take immediate action to enable veterans to get timely access to care from outside the VA system. The nation's largest doctors group also recommended that state medical societies create and make available registries of outside physicians willing to treat vets.
The Senate bill would authorize the VA to lease 26 new health facilities in 17 states and Puerto Rico and spend $500 million to hire more doctors and nurses. The House bill does not include a specific dollar amount, but Miller said the VA would save $400 million annually by eliminating bonuses, money the agency could use for expanded care.
The House and Senate bills would let veterans facing long delays for appointments or living more than 40 miles from a VA facility choose to get care from non-agency providers for the next two years. Some veterans already get outside care, but the process is cumbersome and riddled with delays, veterans and their advocates say.
The Senate bill would make easier to fire top VA officials, although with more employee safeguards than in an earlier, House-passed bill.