In a statement to CBS News, Shinseki said that he had been alerted on Friday to a June 2013 email from David Newman, a registered nurse at the VA Medical Center in Cheyenne, Wyoming. Shinseki asked his agency's office of the inspector general to look into the scheme described in the email, CBS reported.
"I have also directed that the employee be removed immediately from patient care responsibilities and placed on administrative leave," Shinseki said, according to CBS News.
"VA takes any allegations about patient care or employee misconduct very seriously," Shinseki's statement said. "If true, the behavior outlined in the email is unacceptable."
CBS News posted to its website a copy of the email that appeared to be from Newman, who worked as a telehealth coordinator at the VA Medical Center in Cheyenne. Reuters could not immediately confirm the report, and Newman could not be located for contact.
Representatives for the Department of Veterans Affairs did not immediately return calls or an email seeking comment on the report.
The message outlined a technical scheme to ensure patients were recorded as obtaining appointments within a Department of Veterans Affairs' mandated 14-day window, regardless of when an appointment was first requested or how long the patient waited, CBS News reported.
"Yes, it is gaming the system a bit," Newman wrote in the email, according to CBS. The message added that when workers exceed the 14-day measure "the front office gets very upset."
The American Legion veterans group and Republican U.S. Senators Jerry Moran of Kansas and John Cornyn of Texas have called for Shinseki to step down following reports based on whistleblowers' claims that up to 40 veterans died while waiting for appointments or specialist care at the VA hospital in Phoenix.
A congressional committee voted on Thursday to subpoena Shinseki, ordering him to produce all emails and written correspondence sent between April 9 and May 8 related to the disappearance or destruction of a secret patient wait list at the Phoenix hospital.
Shinseki has rejected calls for his resignation.