The review will include FBI Director James Comey's news conference in July and his two letters to the Hill in late October and early November. Comey said in a statement that he is "grateful" that Horowitz is taking on this review.
"He is professional and independent and the FBI will cooperate fully with him and his office. I hope very much he is able to share his conclusions and observations with the public because everyone will benefit from thoughtful evaluation and transparency regarding this matter," Comey said in a statement.
Before the Nov. 8 election, Comey sent a letter to lawmakers that said the FBI would look into new emails related to Clinton. They were found as part of an on-going probe of disgraced former New York congressman Anthony Weiner. The FBI later said it would not change its conclusion.
"Allegations that decisions regarding the timing of the FBI's release of certain Freedom of Information Act (FOIA) documents on October 30 and November 1, 2016, and the use of a Twitter account to publicize same, were influenced by improper considerations," Horowitz said in a statement.
The review comes in response to requests from "numerous Chairmen and Ranking Members of Congressional oversight committees, various organizations, and members of the public," the department said.
The review will not substitute the Office of the Inspector General's judgment for the judgments made by the FBI or the Department regarding the substantive merits of investigative or prosecutive decisions, the department said.
This story is developing. Please check back for further updates.