The agent, Peter Strzok, is considered one of the most experienced and trusted FBI counterintelligence investigators.
Clinton and her supporters say Comey's moves in October cost her the 2016 election, and Trump and his Republican allies have used it to justify Comey's firing - the event that ultimately led to Mueller being appointed as special counsel.
Peter Strzok, a veteran FBI investigator, was shuffled off to the FBI's human resources department by Mueller after the Justice Department's inspector general opened an investigation into the texts, The New York Times reported on Saturday. Page, who was an Federal Bureau of Investigation lawyer before joining the special counsel team, left the team to return to the Federal Bureau of Investigation in July, the special counsel's office confirmed weeks later.
The people discussing the matter did not further describe the political messages between Strzok and Page, except to say the two would sometime react to campaign news of the moment. Page reportedly left Mueller's team in July and no longer works with McCabe, while Strzok was removed from Mueller's team in August and subsequently reassigned to the FBI's HR department in an apparent demotion. Republicans in the House of Representatives have put forward measures to limit the special counsel probe or have called for his ousting or resignation. The messages from Mr. Strzok were discovered in the course of that internal review. But following the news, analysts pointed out that his reassignment suggests that Mueller has worked to avoid any conflicts of interest. A spokeswoman for the Justice Department said that "we are aware of the allegation and are taking any and all appropriate steps".
The Justice Department 's Office of the Inspector General said in a statement Saturday that it has been "reviewing allegations involving communications between certain individuals, and will report its findings regarding those allegations promptly upon completion of the review of them".