Sen. John Ensign, the subject of investigations by the Senate Ethics Committee and the Justice Department tied to his alleged attempts to cover up an extramarital affair, has begun paying legal bills for unidentified members of his staff.

As first reported by the Las Vegas Review-Journal, the Nevada Republican’s office confirmed Friday that payments his campaign made to three law firms in spring 2010 are on the behalf of aides who were contacted by authorities in connection to the investigations. It is not known whether the aides are current or former employees in Ensign’s office.

“Senator Ensign’s campaign is paying for the legal bills accrued by staff as a result of cooperating with the on-going ethics investigation,” Ensign aide Jennifer Cooper said in a statement issued Friday. “Senator Ensign felt strongly that his staff should not be shouldered with the financial burden of this investigation and was told by the Senate Ethics Committee that the only way he could assist in paying for staff legal fees was through the campaign, not through personal or legal defense funds.”

Ensign established a legal defense fund in late May to pay expenses related to both investigations.

The FBI and the ethics committee are separately investigating Ensign’s alleged efforts to cover up an affair with a campaign aide, Cynthia Hampton. She is married to Doug Hampton, Ensign’s top personal office aide at the time of the affair. The Hamptons no longer work for Ensign.

Citizens for Responsibility and Ethics in Washington, a watchdog group, and others have accused Ensign of using his office to steer clients to Doug Hampton’s lobbying business in exchange for his silence about the affair. Hampton told the New York Times last fall that Ensign had taken specific steps to assist his lobbying clients and helped circumvent the lobbying ban that applied to Hampton as the Senator’s former employee.

The Justice Department has begun issuing subpoenas in the Ensign case, including requests for documents from the National Republican Senatorial Committee, where the Senator served as chairman for the 2008 campaign cycle.

Paul Singer contributed to this report.