House Judiciary Committee Chairman Bob Goodlatte and House Oversight Committee Chairman Trey Gowdy said they have "outstanding questions" about why former Federal Bureau of Investigation Director James Comey decided to publicly disclose and keep Congress updated on the status of the bureau's probe into Clinton's handling of classified information, but never disclosed its probe into President Donald Trump's campaign associates.
The probe will also explore the FBI's decision to "appropriate full decision-making" in declining to prosecute Clinton, rather than leaving it to prosecutors at the Justice Department, they said in a statement.
An FBI spokeswoman declined to comment on the probe.
Ian Prior, a Justice Department spokesman, said the department plans to "fully cooperate with this important congressional investigation."
Comey, who was fired by Trump earlier this year, could not be immediately reached for comment.
The joint investigation by the two panels is now the second congressional inquiry into the FBI's handling of the Clinton investigation.
It also comes as Republicans are starting to gear up for midterm elections, after suffering major setbacks in trying to advance legislation to repeal Obamacare.
The Senate Judiciary Committee has also been digging into the matter, as part of a broader probe that also encompasses alleged Russian meddling in the 2016 campaign and whether Trump's campaign associates colluded with the Russians.
In addition, the Justice Department's inspector general is conducting an inquiry into public statements that Comey made about the Clinton investigation.
It is highly unusual for the FBI to confirm or deny the existence of an investigation.
However, Comey discussed the status of the probe in 2016.
In July of that year, he held a press conference and testified about why the FBI opted not to refer Clinton for prosecution.
Then in October, he told Congress he was reopening the matter because of new emails found on the computer of disgraced former Congressman Anthony Weiner, who was married to Huma Abedin, the vice chair of Clinton's campaign.
On Nov. 6, he said a search of Weiner's computer had produced no new evidence.
Comey was later fired by President Trump.
A memo drafted by Deputy Attorney General Rod Rosenstein recommended firing Comey on the basis of his handling of the Clinton matter, but Trump later said he fired Comey over "this Russia thing."
(Reporting by Sarah N. Lynch and Susan Heavey; Editing by Andrea Ricci)
