WASHINGTON — Even before the F.B.I. conducted 550 interviews of officials and seized the phone records of Associated Press reporters in a leak investigation connected to a 2012 article about a Yemen bomb plot, agents had sought the same reporters’ sources for two other articles about terrorism.

In a separate case last year, F.B.I. agents asked the White House, the Defense Department and intelligence agencies for phone and e-mail logs showing exchanges with a New York Times reporter writing about computer attacks on Iran. Agents grilled officials about their contacts with him, two people familiar with the investigation said.

And agents tracing the leak of a highly classified C.I.A. report on North Korea to a Fox News reporter pulled electronic archives showing which officials had gained access to the report and had contact with the reporter on the day of the leak.

The emerging details of these and other cases show just how wide a net the Obama administration has cast in its investigations into disclosures of government secrets, querying hundreds of officials across the federal government and even some of their foreign counterparts.