A senior official at the center of the Department of Veterans Affairs wait list scandal told Congress that he does not believe the documents, which are all believed to have been destroyed, were secret.

The House Veterans Affairs Committee held an uncommon primetime hearing Wednesday evening that extended late into the night to examine the VA's lack of compliance with a May 8 congressional subpoena for documents that lawmakers hope could shine light on a hidden wait list that schedulers allegedly used to manipulate a backlog of veterans waiting for health care.

Dr. Thomas Lynch, M.D., a senior VA official tasked to lead an internal investigation into the accusations, said that the lists, which included about 1,700 veterans, were destroyed in late 2012 through mid-2013 once the patients were rescheduled because they contained confidential "patient identifiable information."

Through more than four hours of testimony, Lynch contended the lists were not intended to be secret, but rather were automatically generated by the VA's scheduling system, known as VistA, to help employees track appointments that needed to be re-booked.

"I did not think they were secret lists," said Lynch, Assistant Deputy Under Secretary for Health for Clinical Operations. "When you cancel a patient, it generates a document that says these are the patients you canceled. It provides information about their Social Security number, the date of their appointment and the time of their appointment so that you can use that information to reschedule the patient."

VA Acting Inspector General Richard J. Griffin released an interim report Wednesday that confirmed scheduling manipulation at the Phoenix VA Medical Center that was "systemic" at facilities throughout the country and risked forgetting or losing track of veterans seeking care.

Lynch said he has made three trips to Phoenix to investigate the alleged misconduct since finding out about the issue on April 9, although he admitted he has not met with any veterans or doctors during his visits.

"We learned during the course of the second visit that the transfer and the use of this document was occurring during the course of rescheduling patients because they were trying to provide care more promptly and because they were trying to consolidate clinic profiles to make the clinic management more efficient," Lynch testified. "Once the rescheduling has occurred, the list is no longer necessary, so it is appropriately destroyed."

Lynch said he did not know specifically which schedulers destroyed the lists, drawing the ire of lawmakers.

"It's important that we identify the people that actually did the destruction of these things," Rep. Dan Benishek, R-Mich., said. "I just don't understand how you can conduct an investigation about the alleged destruction of documents and not actually talk to anybody or know the name of anybody who actually did the destruction."

The VA Inspector General's interim report found that the practices are "systemic" throughout veteran hospitals, and his probe has now expanded to 42 VA facilities throughout the country.

"Veterans' health is at stake, and I will not stand for a department cover-up," House Veterans Affairs Chairman Jeff Miller, R-Fla., said during the hearing. "To fulfill our congressional oversight duties, it is absolutely essential to receive the documents that we have requested from the Department of Veterans Affairs. The scope of the May 8th subpoena was very narrow, and was sufficiently tailored to provide reasonable time to produce the documents in full."

The subpoenas requested the VA produce all emails and written correspondence regarding the destruction or disappearance of alternate or interim wait lists sent and received by 27 various VA officials between April 9 and May 8.

While the committee's ranking Democrat, Rep. Michael Michaud, acknowledged the VA has been more responsive over the past several days, he said he was "not wholly satisfied" with the department's compliance with the committee's investigation.

"I am not happy," Michaud, D-Maine, said. "We do expect answers. We'll get to the bottom of this to uncover the truth and ensure a solution is implemented that never allows something like this to happen again."

After the interim report was released, dozens of Members of Congress called on VA Secretary Eric Shinseki to resign, including Rep. Doug Lamborn, who spoke out during the hearing to demand that the secretary step down.

"I was waiting for information to be gathered to make my judgment and now it is in," Lamborn, R-Colo., said. "Even if the secretary did not know in advance of these wrongdoings - and I don't believe he did - these violations should not have happened on his watch."

While at least 58 Members of Congress, including at least 20 Democrats, have called for Shinseki to resign, one House Republican suggested that President Obama is ultimately responsible for the department's transgressions.

"I think this goes all the way to the desk of the president of the United States," Rep. David Jolly, R-Fla., said.