FBI agents grilled government officials and examined their email and phone logs in an effort to uncover the source of a story on Iran leaked to the New York Times, the newspaper reported.
As the Department of Justice continues to draw heat over its decision to seize the phone records from journalists at the Associated Press, the Times published an article Sunday giving fuller details of other attempts to discover those who had passed on sensitive information to the press.
It claimed that the FBI targeted the same AP reporters currently being investigated over a 2012 article about a Yemeni bomb plot for two other stories relating to terrorism. Meanwhile, a separate probe into the leaking of a CIA document on North Korea to Fox News had seen agents pull electronic data from officials, detailing who had access to the dossier and who had contact with reporter James Rosen.
The investigations into Fox News and AP stories have in recent weeks sparked protest from sections of the media, suggesting it amounts to clear government overreach. Last weekend, Associated Press's president and CEO Gary Pruitt condemned the Justice Department's actions as "unconstitutional".
Pruitt added that the probe had already had a chilling effect.
"Officials that would normally talk to us and people we talk to in the normal course of news-gathering are already saying to us that they are a little reluctant to talk to us. They fear that they will be monitored by the government."
On Sunday, the New York Times claimed that monitoring of email logs and phone records had taken place over an article it published on the White House's role in computer attacks on Iran's nuclear enrichment facilities.
The newspaper said FBI agents asked the White House, the Defence Department and intelligence agencies for communication logs from author of the article, Times reporter David Sanger.
But unlike in the cases of AP and Fox News, in which records were seized without prior warning to those targeted, the New York Times investigation focused on the records of officials who handed over the information, rather than the journalist, according the Times report.