FoxNews.com investigative reporter Malia Zimmerman told Fox News' "The O'Reilly Factor" Thursday evening that former national security adviser Susan Rice left "a very extensive paper trail" of unmasking requests related to members of President Trump's transition team.

"Every time they go into the system, from what I’m told, there’s a log, there’s a record of that," Zimmerman told host Bill O'Reilly. "And so, that would provide the date of the document, what it was regarding, and the name that was supposed to be unmasked through that process.

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"So, it's probably a gold mine of information if the House and Senate [intelligence committees] can get it."

Zimmerman added that U.S. intelligence agencies had been "stonewalling" lawmakers following a public hearing into Trump's "wiretapping" allegations last month.

"During that hearing, there were 100 questions that weren’t answered and they were supposed to come back into private session and that was never done," Zimmerman said. "And there’s been, from what we were told, all kinds of excuses as to why [FBI Director] James Comey hasn’t come back, and really no response on several of the questions."