The FBI sent to Congress Tuesday 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, according to US officials briefed on the matter.
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, or SCIF. And due to its confidential status, it cannot legally be shared with the public.
It's being shared with Congress "with the expectation it will not be disseminated or disclosed without FBI concurrence," the bureau said in a statement.
"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.
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."
The letter also says others who engaged in the same type of behavior as Clinton would be potentially subject to "severe administrative consequences."
In a statement, the Clinton campaign called for the notes to be released publicly.
"This is an extraordinarily rare step that was sought solely by Republicans for the purposes of further second-guessing the career professionals at the FBI," the campaign said. "We believe that if these materials are going to be shared outside the Justice Department, they should be released widely so that the public can see them for themselves, rather than allow Republicans to mischaracterize them through selective, partisan leaks."
'A desperate attempt'
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.
CNN's Jake Tapper had reported Sunday that lawmakers would soon receive the notes on Clinton's three-hour interview with the FBI.
Cummings, who released the letter to CNN, blasted what he views as Republicans' political motivations in seeking the report.
"The FBI already determined unanimously that there is insufficient evidence of criminal wrongdoing," Cummins said in a statement. "Republicans are now investigating the investigator in a desperate attempt to resuscitate this issue, keep it in the headlines, and distract from Donald Trump's sagging poll numbers."
A political headache for Clinton
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.
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.
Comey said last month that the agency found "thousands" of emails from Clinton's server that were work-related and deleted and had not been turned over to the State Department. State will conduct its own review to determine whether any of the emails are personal, and any that are will not be released. Personal emails are not deemed "agency records" and therefore are not subject to release under the Freedom of Information Act.
Congressional Republicans, meanwhile, are intent on forcing Clinton to pay a political price -- with Reps. Jason Chaffetz, R-Utah, and Bob Goodlatte, R-Virginia, calling Monday in a letter for the Justice Department to charge Clinton with perjury over her sworn testimony to the House's Benghazi committee.
In at least four separate occasions during a marathon appearance before the House Select Committee on Benghazi, the lawmakers alleged the former secretary's claims were at odds with what the FBI has now discovered to be the truth about her private server.
"The evidence collected by the (FBI) during its investigation of Secretary Clinton's use of a personal email system during her time as secretary of state appears to directly contradict several aspects of her sworn testimony," they wrote.
CNN's Deirdre Walsh and Dan Merica contributed to this report.
By Evan Perez, Shimon Prokupecz and Eric Bradner