The move came after the Justice Department began probing whether the agent had sent anti-Trump text messages.
An FBI official assigned to Special Counsel Robert S. Mueller III's probe of Russian interference in the 2016 election was removed this summer after his bosses discovered texts shared with another official attacking President Donald Trump.
But Mr. Strzok was reassigned this summer from Mr. Mueller's investigation to the F.B.I.'s human resources department, where he has been stationed since.
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.
Peter Strzok, as deputy head of counter-intelligence at the FBI, was a key player in the investigation into Clinton's use of a private email server to do government work as Secretary of State, as well as the probe into possible coordination between the Trump campaign and Russian Federation in the 2016 election.
A spokesperson for Mueller's office said, "Immediately upon learning of the allegations, the special counsel's office removed Peter Strzok from the investigation". Page left Mueller's team weeks before news of the text messages broke, Carr added.
Justice Department spokeswoman Sara Isgur Flores said in an email that "we disagree with the chairman's characterization and will continue to work with congressional committees to provide the information they request consistent with our national security responsibilities".
"And "ANTI-TRUMP FBI AGENT LED CLINTON EMAIL PROBE" Now it all starts to make sense!"
The text messages showed Strzok and Page reacting with anti-Trump sentiments to certain news events, including the presidential debates. However, the Federal Bureau of Investigation does allow its agents to express opinions "as an individual privately and publicly on political subjects and candidates".
The House committee's top Democrat, Rep. Adam Schiff of California, responded in a statement that the Department of Justice inspector general is "properly investigating the handling of the investigation, including the current allegation of bias" by Strzok. One of the sources said the probe will be completed by "very early next year".
One of the only times I've ever seen my father, a career military man and Vietnam veteran, express genuine concern over the direction of our country was in the wake of the FBI's fall from grace under James Comey. But in August, news outlets reported that he was no longer involved in the special counsel effort. Mueller has been looking into Russian interference in the 2016 USA presidential election since May.