Washington (CNN) Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein are interviewing four potential interim FBI directors Wednesday, according to a Justice Department official.

Deputy Director Andrew McCabe assumed the position of acting director of the FBI on Tuesday by statute after James Comey was fired, and is one of those under consideration for interim director as well, the official explained.

The official said the four people Sessions and Rosenstein plan to interview on Wednesday include:

The official said a formal announcement of the decision should come soon -- later Wednesday or Thursday.

Speculation began almost immediately Tuesday over President Donald Trump pick for Comey's replacement, but the Justice official said not to expect politicians like former New York City Mayor Rudy Giuliani to be tapped the interim post. Giuliani later confirmed to CNN he is not under consideration.

And while CNN is told the candidates are not only limited to FBI officials, the Federal Vacancies Reform Act governs the categories of individuals who are eligible serve as the interim director, and the official said that Sessions and Rosenstein are looking for someone with significant law enforcement experience.

As to why DOJ officials are bothering to interview candidates for an interim replacement -- instead of simply keeping McCabe in place -- the department official suggested that it is not unusual to interview other people when there is a vacancy.

Yet choosing McCabe would come with baggage.

Not only was he at the bureau during Hillary Clinton's private email server investigation, but DOJ's Office of Inspector General is currently investigating whether he should have recused himself from that investigation because of campaign contributions his wife received from Clinton ally and current Virginia Gov. Terry McAuliffe.

If McCabe is not kept as the interim replacement for the top spot at FBI, he is expected to stay on as deputy director.

The official also shed light on the timing of Comey's ouster this week.

In a memo to Sessions on Tuesday, Rosenstein outlined his case for why Comey made "serious mistakes" in his handling of Clinton's email investigation last year, but according to the Justice official, Comey's testimony to Congress last week sealed the deal.

Comey explained last week that while the idea of impacting the election made him "mildly nauseous," he would not change what he did.

He also indicated that the now-infamous tarmac meeting between then-Attorney General Loretta Lynch and former President Bill Clinton was the crucial "capper" that, in his view, irreparably damaged the independence of the Clinton investigation.

"That was a hard call for me to make, to call the attorney general that morning and say: 'I'm about to do a press conference and I'm not going to tell you what I'm going to say. And I said to her, 'I hope you'll understand someday why I think I have to do this,'" Comey told senators.

Yet his refusal to appear unrepentant in refusing to follow typical DOJ protocols and chain of command only further underscored why he must be fired, according to the department official and the White House.

"That's simply not allowed," deputy press secretary Sarah Huckabee Sanders told reporters at Wednesday's press briefing.