During the same interview with the F.B.I., Mr. Wolfe denied knowing Ms. Watkins. But confronted with pictures of the two together, he admitted being in a “personal relationship” with her since 2014.
Ms. Watkins said she told editors at BuzzFeed News and Politico about it and continued to cover national security, including the committee’s work. Ben Smith, the editor in chief of BuzzFeed News, said in a statement, “We’re deeply troubled by what looks like a case of law enforcement interfering with a reporter’s constitutional right to gather information about her own government.”
A Politico spokesman, Brad Dayspring, said that the situation was “managed accordingly” after Ms. Watkins disclosed the matter, and that her beat was national security and law enforcement, not solely the committee, which other reporters primarily covered.
Ms. Watkins also told editors at The Times about the previous relationship when she was hired to cover federal law enforcement.
Attorney General Jeff Sessions said last year that the Justice Department was pursuing about three times as many leak investigations as were open at the end of the Obama administration. Under Mr. Obama, the Justice Department prosecuted more leak cases than all previous administrations combined.
“The attorney general has stated that investigations and prosecutions of unauthorized disclosure of controlled information are a priority of the Department of Justice,” John Demers, a top Justice Department official, said in a statement announcing Mr. Wolfe’s arrest.
The investigation came to light after the Senate Intelligence Committee made a cryptic announcement on Wednesday that it was cooperating with the Department of Justice “in a pending investigation.” Earlier, the Senate quietly and unanimously adopted a resolution to share committee information with the Justice Department “in connection with a pending investigation arising out of the unauthorized disclosure of information.”