At least one company and the National Republican Senatorial Committee have been issued subpoenas requesting documents in a federal grand jury investigation related to Sen. John Ensign, R-Nevada.
The Senate Ethics Committee also is investigating Ensign, who has been dogged by allegations of improper conduct stemming from an affair with the wife of a former aide. An Ethics Committee spokesman has declined to comment on precisely what its members are looking into.
A spokesman for the NRSC, which works to elect Republicans to the U.S. Senate, said the organization had received a subpoena related to Ensign.
Another NRSC official, general counsel Sean Cairncross, would not confirm that the subject of the subpoena was Ensign, but he noted that the 2008 election was cycle was the time when Ensign chaired the committee.
"NRSC has responded appropriately to questions concerning matters related to the 2008 election cycle timeframe," Cairncross said.
The U.S. Attorney's office had no immediate comment. Neither did Ensign's staff.
A source from one of the companies linked to the probe into Ensign's business dealings told CNN that the company had been issued a subpoena to produce documents to a federal grand jury.