An explosive announcement Thursday revealed the U.S. Justice Department's inspector general has launched an investigation into the FBI's handling of Hillary Clinton's use of a private, unsecured email while she served as secretary of state.

And three of the people targeted in the investigation include FBI Director James Comey, Deputy Director Andrew McCabe and a Justice Department official who leaked secrets to Clinton campaign chairman John Podesta.

It's rare for the inspector general to publicly disclose investigations, but Justice Department Inspector General Michael Horowitz did just that Thursday when he announced the probe in a statement. Horowitz said the Justice Department will look into "allegations that department and FBI employees improperly disclosed non-public information" and whether McCabe should have recused himself from the Clinton email probe.

As WND reported, McCabe oversaw the FBI’s investigation of Clinton's handling of classified information and use of the private email server. He did so despite the fact that his wife, Dr. Jill McCabe, had received $675,000 in contributions from longtime Clinton adviser and fundraiser Terry McAuliffe, who is governor of Virginia.

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At the time, Sen. Richard Black, R-Va., said McCabe should have immediately recused himself from the Clinton probe.

“As an attorney, and a former JAG officer who has had responsibilities over the investigation and prosecution of crimes, I am at a loss to see how the FBI could possibly allow Andrew McCabe to oversee the investigation of Mrs. Clinton’s email server scandals,” Black said in a statement just weeks before the November election. “Mr. McCabe was clearly indebted to the Clinton campaign because of the support given his wife.”

Black noted Clinton’s “defense against charges that she has lawlessly handled classified information in her emails, and by using her private email server, has been that the FBI performed a complete investigation and found no violation of law.”

“I was astonished at how much money she was able to raise – $1.8 million. How convenient for your husband to be a high-ranking FBI official with lots of potential influence,” he said.

The Trump campaign called on the FBI to address the issue.

“The fact that this was allowed to occur shows either outright negligent behavior by the FBI or a level of corruption that is beyond belief,” Trump senior policy adviser Jason Miller told the Washington Times. “The FBI needs to fully address these issues as soon as possible.”

Also, in May 2015, a top Justice Department official leaked information to Clinton's team about the ongoing legal case. Assistant Attorney General Peter Kadzik sent a message from his private email account to Podesta, tipping him off that the government was attempting to delay posting Clinton's emails until 2016 and warning of an impending House hearing in which a Justice Department official would be questioned about the emails.

"DOJ folks inform me there is a status hearing in this case this morning, so we could have a window into the judge's thinking about this proposed production schedule as quickly as today," wrote Clinton spokesman Brian Fallon in a May 2015 email published by WikiLeaks. Fallon is a former Justice Department spokesman.

When news broke of the communication, Republicans accused Clinton and the Justice Department of "collusion."

“Emails showing the Department of Justice was giving Hillary Clinton’s campaign inside information about an ongoing investigation into her email server is deeply disturbing and raises even more questions about Bill Clinton’s tarmac meeting with Attorney General Loretta Lynch,” then-RNC Chairman Reince Priebus said in an October statement.

As for Comey, the FBI director angered half the country on July 5 when he closed the criminal investigation of Clinton four months before the election, despite acknowledging she lied to the agency, lied about not passing classified information on her personal, unsecured server and broke counter-espionage laws for which others are serving prison time. Then he got the other half of the country angry at him when he reopened the criminal investigation in the last week of October. Then, amid pressure from the Justice Department and, reportedly, from President Barack Obama, Comey closed the case again on Nov. 6, just two days before the election.

President-elect Donald Trump has not indicated whether he plans to allow Comey to remain in his position as FBI director. However, the results of the inspector general's investigation could give Trump justification to fire Comey.

In a letter sent to House and Senate committee leaders, Comey said FBI agents had completed their review of all messages to or from Clinton on a laptop seized from former Rep. Anthony Weiner, the estranged husband of a Clinton aide, and had found nothing worthy of prosecution.

“Based on our review, we have not changed our conclusions that we expressed in July with respect to Secretary Clinton,” Comey wrote. “I am very grateful to the professionals at the FBI for doing an extraordinary amount of high-quality work in a short-period of time.”

Clinton spokesman Brian Fallon accused Comey of sabotaging Clinton's chances of becoming president with his announcement.

"The deviations from the protocols at the FBI and the Justice Department were so glaring and egregious," Fallon said in an interview on MSNBC.

Horowitz, an Obama appointee and a Democratic Party contributor, said the inspector general investigation comes after the DOJ received requests “from numerous chairmen and ranking members of congressional oversight committees, various organizations, and members of the public."

The White House said it had no role in the inspector general's decision to investigate the FBI's handling of the case.

“Decisions that are made by inspectors general across the administration are independent," White House spokesman Josh Earnest said Thursday. “Hopefully they will follow the evidence where it leads.”

In a statement to MSNBC, Comey said he welcomes the inspect general investigation.

"I am grateful to the Department of Justice's IG for taking on this review," he said. "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."