Recipients of subpoenas issued in the Justice Department investigation tied to Sen. John Ensign (R-Nev.) include several Nevada firms that donated to the National Republican Senatorial Committee during Ensign’s tenure as chairman, as well as his former top aide, CBS affiliate KLAS-TV reported Thusday.

The NRSC also acknowledged publicly Thursday that it has received a subpoena for documents in the investigation, which is believed to be focused on Ensign’s efforts to secure lobbying work for former aide Douglas Hampton. Hampton left the Senator’s staff after Ensign ended an affair with Hampton’s wife, Cynthia Hampton. A $96,000 payment that Ensign’s parents made to the Hamptons may also be under review.

The station’s Web site identified executives at the tech firms eCommLink, Selling Source and Pay Card USA, who Ensign allegedly pushed for contributions to the NRSC.

The station also identified subpoenas issued by the Senate Ethics Committee, which is reviewing the matter, including former Nevada state lawmaker Pete Ernaut, now with R&R Partners, the lobbying firm that hired former Ensign Chief of Staff John Lopez. The station reported that Lopez has also been served with subpoenas. Lopez referred questions from Roll Call to his attorney Thursday, who did not immediately return a telephone call for comment.

The station noted the firms and their executives have not been accused of wrongdoing. The investigations are believed to focus on whether Ensign assisted his one-time top aide in secure lobbying clients, which could determine if he violated the Senate’s one-year revolving-door ban.

According to a redacted copy of one subpoena obtained by KLAS-TV on Wednesday, the DOJ is also seeking any documents — including calendars, e-mails, photographs, notes, memorandums and other items — that mention Ensign, the Hamptons or Lopez and any contacts with Ensign’s staff.

The subpoenas also seeks any documents that reference Michael and Lindsey Slanker. Michael Slanker, a former Ensign political lieutenant, is the founder of November Inc., a lobbying firm that hired Hampton after he left Ensign’s office. Ensign is reported to have coordinated Hampton’s move to the firm and helped him secure clients including Allegiant Air and NV Energy.

Michael Slanker has also managed Ensign’s Senate bids and served as the NRSC’s political director under Ensign during the 2008 election cycle. His wife, Lindsey, served as the NRSC’s finance director that same cycle.