Hillary Clinton
Hillary ClintonReuters

The FBI on Tuesday sent to Congress a report the bureau provided to the Justice Department last month to explain why it recommended no charges in the Hillary Clinton email server investigation, CNN reports.

The decision to provide the investigative material on a case in which charges were not brought is exceedingly rare. The report includes notes from the interviews of Clinton and other witnesses in the investigation.

The notes, called 302s, represent an FBI agent's memos on the interviews and will be provided along with other investigative material.

The material is designated classified so it will need to be reviewed by congressional officials in a Sensitive Compartmented Information Facility (SCIF). And due to its confidential status, it cannot legally be shared with the public.

"The FBI conducted this investigation, as it does all investigations, in a competent, honest and independent way," FBI acting Assistant Director Jason V. Herring wrote in a letter to House Oversight Committee Chairman Rep. Jason Chaffetz and the committee's ranking Democratic member, Maryland Rep. Elijah Cummings, according to CNN.

The letter reiterates FBI Director James Comey's assertion last month that it was not clear whether Clinton deliberately received classified information on her private email server.

"As the director stated, the FBI did find evidence that Secretary Clinton and her colleagues were extremely careless in their handling of certain, very sensitive, highly classified information," the letter said.

"The term 'extremely careless' was intended to be a common sense way of describing the actions of Secretary Clinton and her colleagues. The director did not equate 'extreme carelessness' with the legal standard of 'gross negligence' that is required by the statute. In this case, the FBI assessed that the facts did not support a recommendation to prosecute her or others within the scope of the investigation for gross negligence," it added.

A day after Comey announced he would recommend that Clinton not be indicted for the private email affair, U.S. Attorney General Loretta Lynch accepted the recommendation.

Tuesday’s letter also says others who engaged in the same type of behavior as Clinton would be potentially subject to "severe administrative consequences."

The interviews in the Clinton email case were voluntary and the FBI practice is to not have recorded or transcribed, but instead to have them "memorialized" with notes taken by an FBI agent.

Clinton's top aides made clear that they would like those notes to be released publicly versus, as one aide put it, "released piecemeal by people with motive."

"We would prefer the entire document to be released," the aide said, according to CNN.

It's the latest development in the controversy over Clinton's private email server, which she used during her tenure as President Barack Obama's secretary of state.

Clinton has said she used private emails out of "convenience", though she has also admitted it "would have been better" to have two accounts to separate work and personal emails.

The State Department has also agreed in a court filing to turn over more emails, which were recovered after Clinton turned over her private server, to the conservative organization Judicial Watch, which is suing for the emails.

The State Department has not said whether it will release these emails to the public, as it did with the nearly 55,000 pages of work-related emails Clinton provided last year.