Four reporters have testified in the investigation: Glenn Kessler and Walter Pincus of The Washington Post, Tim Russert of NBC News and Matthew Cooper of Time magazine. In their testimony, all four discussed their interactions with I. Lewis Libby, Vice President Dick Cheney's chief of staff. Mr. Pincus has also testified about a conversation with a second source, whose identity is not known. Mr. Cooper testified for a second time on Wednesday, about a conversation with Mr. Rove. All of the reporters said they testified with their sources' permission.

...Mr. Kessler and Mr. Pincus said they did not discuss Ms. Wilson with Mr. Libby, and Mr. Cooper has not spoken publicly on the issue.

Mr. Russert's testimony last August provides intriguing clues. A statement issued by NBC at the time suggests that Mr. Libby had told Mr. Fitzgerald that he had heard about Ms. Wilson from Mr. Russert.

According to the statement, lawyers for Mr. Russert and Mr. Fitzgerald reached an agreement under which Mr. Fitzgerald questioned Mr. Russert only about Mr. Russert's end of a conversation in early July 2003 with Mr. Libby. That would be an unusual way to go about pursuing a leak inquiry, but it is consistent with an attempt to try to establish that Mr. Russert provided information to Mr. Libby.

Mr. Russert, however, according to the NBC statement, said ''he did not know Ms. Plame's name or that she was a C.I.A. operative and that he did not provide that information to Mr. Libby.'' Indeed, the statement said, Mr. Russert first learned the information from Mr. Novak's column.