Top FBI investigator reassigned from Mueller's Russia probe -- just as investigation gathers steam

A high-ranking FBI official who was tapped to assist Special Prosecutor Robert Mueller in his probe in President Donald Trump, the Trump 2016 campaign and White House transition team's connections to Russia has abruptly left the investigation, the Hill reported Wednesday.

ABC News identified the departing agent as Peter Strzok and said he has been reassigned to the bureau's human resources division.

Strzok is known as a veteran investigator and was one of the leaders of the FBI probe into former Democratic presidential candidate Hillary Clinton's use of a private email server during her time as U.S. Secretary of State. He reportedly went straight from that investigation into the Russia probe.

No reason has been offered for Strzok's departure.

The announcement comes just as Mueller's investigation appears to be heating up. Last week, news surfaced that the FBI had executed a pre-dawn raid on the home of former Trump 2016 chairman Paul Manafort.