Hillary Clinton told the FBI she could not recall answers to some of their questions about her secret server scandal because she had been concussed in 2012.

The extraordinary disclosure was made as the FBI published details of its agents' interview with the former secretary of state which was conducted days before the agency's director ruled out any charges against her.

Agents noted that Clinton could not recall being trained to handle classified materials as secretary of state, and had no memory of anyone raising concerns about the sensitive information she received at her private address.

The Democratic presidential nominee also 'did not recall receiving any emails she thought should not be on an unclassified system,' the FBI's report declared.

She did not recall all of the briefings she received on handling sensitive information as she made the transition from her post as secretary of state, due to a concussion she suffered in 2012.

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'CANNOT RECALL': Hillary Clinton appears to have repeatedly deployed a bewildering answer to the FBI's questions in an interview that was not recorded or conducted under oath

The claim will only fuel questions over her underlying health.

The extraordinary defense was revealed in the FBI's account of agents' interview with the Democratic presidential candidate.

'Clinton said she received no instructions or direction regarding the preservation or production of records from (the) State (Department) during the transition out of her role as Secretary of State in 2013,' the FBI files say.

'However, in December of 2012, Clinton suffered a concussion and then around the New Year had a blood clot (in her head).

Clinton leaves New York Presbyterian Hospital accompanied by husband Bill and daughter Chelsea in January 2, 2013. She hadn't been seen in public since Dec. 7 and was receiving treatment for a blood clot

'Based on her doctor's advice, she could only work at State for a few hours a day and could not recall every briefing she received,' the report said.

According to the report, Clinton told the FBI that she did not set up a private email server to sidestep the law requiring her to keep her business communications a matter of public record.

Clinton has claimed it was public knowledge to many State Department employees that she was using a private server because they received emails from her email domain.

But State Department employees interviewed by the FBI said many emails from Clinton appeared to be from 'H' and did not show her private email domain.

The documents also show that Clinton contacted former Secretary of State Colin Powell in 2009 to ask about his use of a personal BlackBerry phone.

In his reply to Clinton via email, Powell told Clinton to 'be very careful' because the work-related emails she sent on her BlackBerry could become public record.

'I got around it all by not saying much and not using systems that captured the data,' Powell said.

And the FBI files also showed how she passed the buck to her former State Department underlings, saying she relied on their judgment when deciding what was and wasn't appropriate to send through her homebrew private email server while she was America's top diplomat.

'She relied on State [Department] officials to use their judgment when emailing her and could not recall anyone raising concerns with her regarding the sensitivity of the information she received at her email address,' the FBI's account reads.

Key verdict: James Comey, the FBI director, ruled that Clinton should not be charged

Keep it out of public records: Powell told Clinton to 'be very careful' because the work-related emails she sent on her BlackBerry could become public record, she revealed

Clinton told investigators she was unfamiliar even with basic markings of confidential materials, such as the (C) markings that denote confidential material portions of emails.

Clinton 'stated she did not know what the (C) meant at the beginnings of the paragraphs and speculated it was referencing paragraphs marked in alphabetical order,' according to the documents.

The FBI documents state that on February 9, 2016, the Justice Department asked Clinton's lawyers at Williams & Connelly to turn over the 13 mobile devices she used over the time period.

The lawyers couldn't locate any of them, and the FBI was 'unable to acquire or forensically examine any of these 13 mobile devices.'

The agency also recounts the improvised way Clinton's private email server came into creation.

Initially, aide Justin Cooper contacted Apple and had a company tech install a server in the basement of the Clinton's Chappaqua home in 2008. The FBI wasn't able to obtain records of the installation from either party.

By 2009, a decision was made to switch to another server because the first was 'antiquated.' Campaign aide Brian Pagliano was brought in for upgrades using leftover equipment from Clinton's presidential campaign.

The original Apple server 'was repurposed to serve as a personal computer for household staff.'

'IS THIS REALLY FROM YOU?' Clinton feared a potential email scam when a known associate sent a link to a web site with porn material, according to the FBI report

Clinton could only work at State for 'a few hours a day' after hitting her head and suffering a concussion during a fall. She 'could not recall every briefing she received'

LETTER OF THE LAW: Clinton stated that she 'did not know' that '(C)' stood for 'CONFIDENTIAL' in classification markings

WHICH ONE IS THIS? Clinton had no fewer than 13 wireless devices, it was revealed – but the FBI wasn't able to acquire any of them as part of its investigation

Republican Donald Trump, who participated in a roundtable discussion Friday, said Clinton's answers 'defy belief'

Eventually a third party, Platte River Networks of Denver, was brought in to manage a third server.

The decision to release the information was made earlier this week in response to several Freedom of Information act requests, and amid mounting pressure to explain the decision not to charge Clinton with a crime related to her mishandling of classified documents.

A written account of the interview, which was neither tape recorded or conducted under oath, was made by agents afterwards and informed FBI Director James Comey's decision not to recommend a Department of Justice prosecution.

The FBI said in a statement Friday that it edited portions of it in accordance with FOIA laws.

'Appropriate redactions have been made for classified information or other material exempt from disclosure,' the agency said.

The FBI provided some portions of its investigative file to members of Congress in August.

The FBI notes disclose: 'Clinton did not recall receiving any emails she thought she should not be on an unclassified system.

'She relied on State official to use their judgment when emailing her and could not recall anyone raising concerns with her regarding the sensitivity of the information she received at her email address.'

The notes also revealed how Clinton said that she simply did not know what markings which told her material was classified were.

The (C) markings were found in several emails on her secret server after an FBI forensic search.

'Clinton stated she did not know and could only speculate it was referencing paragraphs marked in alphabetical order,' the FBI notes said.

Republican House Speaker Paul Ryan issued a statement saying the documents show Clinton's 'reckless and downright dangerous handling of classified information.'

'They also cast further doubt on the Justice Department's decision to avoid prosecuting what is a clear violation of the law,' Ryan said. 'This is exactly why I have called for her to be denied access to classified information.'

Clinton told investigators that she directed her aides in early 2009 to create a private email account and that it was 'a matter of convenience' for it to be moved onto a system maintained by her husband's staff.

She told investigators that 'everyone at State knew she had a private email address because it was displayed to anyone with whom she exchanged emails,' according to a summary of the July 2 interview released Friday.

Clinton said that when top staff received an email, the recipient would evaluate whether the information should be forwarded to her, but that no one at the State Department raised concerns about her using a private email account or server and said no one on her staff 'ever expressed a concern regarding the sensitivity of the content of these emails.'

Another passage states that the FBI 'found that 17,448 emails were not included in the State Department's release of emails' – meaning they didn't get turned over for review.

20-20 HINDSIGHT: Clinton has expressed regret for her private email server in interviews. But when she spoke to the FBI, she said there were multiple aspects of the email setup she could not recall

Clinton wasn't completely oblivious to computer security. At one point, she received an email from a State employee containing a link with potentially malicious software, according to the FBI. Clinton responded: 'Is this really from you? I was worried about opening it!'

According to the FBI, an aide identified as Abedin – no doubt longtime Clinton aide Huma Abedin – sent an email to an unidentified official stating that Clinton was worried that someone was hacking inter her email.

The email was from a known [blank] associate 'containing a link to a website with pornographic material.' In fact, clicking on the link would have sent information to three computers, including one in Russia, according to the documents.

Clinton's GOP rival Donald Trump – who has gone after 'Crooked Hillary' for corruption while also questioning her 'stamina,' released a statement Friday afternoon saying her statements 'defy belief.'

'I was absolutely shocked to see that her answers to the FBI stood in direct contradiction to what she told the American people. After reading these documents, I really don't understand how she was able to get away from prosecution,' said Trump.

'While her use of a single email account was clearly a mistake and she has taken responsibility for it, these materials make clear why the Justice Department believed there was no basis to move forward with this case,' said Clinton campaign spokesman Brian Fallon.

'Clinton's answers either show she is completely incompetent or blatantly lied to the FBI or the public,' said Republican National Committee chairman Reince Priebus. 'Either way it's clear that, through her own actions, she has disqualified herself from the presidency.'

Clinton didn't have a computer on her desk on the 7th floor of the State Department. She did, according to the FBI, sometimes bring her Blackberry or ipad into a secure area of State's 'Mahogany Row' where such devices are prohibited. Three diplomatic security agents told the FBI that Clinton stored her Blackberry in a desk drawer inside the secure area.

The documents state that Abedin stated that Clinton left the secure area to check her email, sometimes doing so on the agency's 8th floor balcony – which has a sweeping view of the Lincoln Memorial.