The Obama administration investigated Fox News reporter James Rosen as a probable "co-conspirator" in connection to a criminal espionage case.

The Justice Department has eyes and ears on Fox's chief Washington correspondent, "at the very least, either as an aider, abettor and/or co-conspirator" in a 2010 espionage case against State Department security adviser Stephen Jin-Woo Kim.

The Washington Post was the first to report the news on Monday, after the accusation appeared in a court affidavit that the publication obtained.

Kim was charged with handing over a classified government report in June 2009 that said North Korea would probably test a nuclear weapon in response to a United Nations sanction condemning previous tests. Rosen reported the news on June 11 in an article published under the headline North Korea Intends to Match UN Resolution With New Nuclear Test.

The CIA learned the information Rosen wrote was obtained from sources inside North Korea. Rosen is the author of the article at the center of the government investigation. The FBI seized all of Rosen's phone records and email correspondents with Kim, taking them in as evidence in the case. The bureau also used security badge records to track his movements to and from the State Department.

In court documents, FBI agent Reginald Reyes described how Kim and Rosen moved in and out of State Department headquarters a few hours before the story was published on June 11, 2009. Reyes wrote there was evidence that Rosen broke the law and allegedly used a "covert communications plan" to exchange information back and forth with Kim. The two even reportedly used alias names in their correspondents.

Kim was indicted in August 2010 on charges of violating the Espionage Act of 1917, meant to prosecute suspected government spies.

Fox News issued a statement on Monday calling the incident "downright chilling."

"We are outraged to learn today that James Rosen was named a criminal co-conspirator for simply doing his job as a reporter," Michael Clemente, Fox News executive vice-president of news, said in the statement. "In fact, it is downright chilling. We will unequivocally defend his right to operate as a member of what up until now has always been a free press."