The discovery could also undermine the integrity of Mueller’s expansive investigation. That’s because Strzok is the FBI agent picked in July 2016 to supervise the then-fledgling investigation into possible collusion between the Trump campaign and Russian government.

Strzok’s central role in the probe is already raising questions about how and why the collusion investigation was opened in the first place.

Carter Page, a former Trump campaign adviser targeted in the early stages of the investigation, told TheDC on Sunday that he is “curious…whether [Strzok’s] fingerprints” are on a secret surveillance warrant taken out against him in Sept. 2016, just after he left the Trump team.