Three officials at the Phoenix Veterans Affairs center where key data allegedly was concealed while dozens of veterans died waiting for care have been placed on leave, the Department of Veterans Affairs said Thursday.

Phoenix VA Health Care System Director Sharon Helman, Associate Director Lance Robinson and a third employee, whose name was not immediately released, were placed on leave as authorities probe allegations that VA officials kept a fake waiting list that made it appear sick veterans were being treated in a timely manner – while hiding the real list that showed up to 1,600 sick veterans were waiting months to see a physician.

“We take these allegations very seriously,” Secretary of Veterans Affairs Eric K. Shinseki said in a statement released late Thursday afternoon. “We believe it is important to allow an independent, objective review to proceed. These allegations, if true, are absolutely unacceptable and if the Inspector General’s investigation substantiates these claims, swift and appropriate action will be taken.”

It was not immediately clear whether the officials were placed on leave with pay. Messages left with VA officials by FoxNews.com on Thursday were not immediately returned.

The Phoenix VA has been under fire since the chairman of the House Veterans Affairs Committee, Rep. Jeff Miller, R-Fla., said on April 9 that up to 40 patients may have died because of care delays and that the hospital kept a secret list of patients waiting for appointments to hide delays in treatment.

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The U.S. Office of Inspector General is investigating the allegations, which come amid problems at other VA hospitals across the country. Patients are being forced to wait weeks and months to see doctors, and in some cases, dying before their appointments. In the past year, VA facilities in South Carolina, Florida, Georgia and Washington state have been linked to delays in patient care or poor oversight.

Also on Thursday, Miller pressed Shinseki to provide a date for when a so-called “interim list” concerning patients was allegedly destroyed, while also asking why the VA did not issue an order prohibiting the destruction of documents until more than a week after a Congressional request.

“I would like to know why it took so long to issue the directive given my public request at a Congressional hearing, the formal request letter to you, and most importantly, the explosive nature of the allegations regarding the deaths of veterans while waiting for care,” he wrote.

FoxNews.com’s Karl de Vries, Cristina Corbin and The Associated Press contributed to this report.