Some of the classified information Hillary Clinton discussed in emails sent on her private server appears to have centered around planned drone strikes and attacks against US/NATO soldiers in Afghanistan, according to 58 pages of documents released by the FBI Friday detailing the bureau's investigation into the Democratic presidential candidate's email practices.

"After reviewing an email dated [redacted], with subject line [redacted], Clinton stated she did not remember the email specifically. Clinton stated deliberation over a future drone strike did not give her cause for concern regarding classification," the FBI's memorandum said, suggesting that Clinton's responses to specific questions she was asked during a 3-hour interview at FBI headquarters July 2 centered around classified information contained in her emails about the Obama administration's targeted killing program. "Clinton understood this type of conversation as part of the routine deliberation process ... Clinton believed the classification level of future drone strikes depended on the context."

In addition to the memo summarizing the FBI's investigation, the bureau released 11 pages of notes detailing an interview conducted with Clinton. The documents were released in response to Freedom of Information Act requests, including one filed by VICE News.

In a statement, Clinton's campaign spokesman, Brian Fallon, said Clinton's camp is "pleased" the FBI released the documents.

"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," Fallon said.

Additional classified information exchanged with Clinton over email appears to support Fallon's claim made earlier this year that the info had already appeared in newspaper articles. Indeed, the FBI's memorandum said Clinton was questioned about an August 25, 2010 email containing a New York Times story about an aide to Afghanistan President Hamid Karzai who was caught up in a corruption scandal and who had been working for the CIA.

"Clinton said she did not remember the email specifically," the FBI's memorandum said. "Clinton stated she was not concerned the displayed email contained classified information," a response she gave the FBI numerous times when she was shown emails she sent and received that contained classified information.

The FBI memorandum, titled "Mishandling of Classified — Unknown Subject or Country (SIM)" said Clinton did not know what certain classification markings on documents meant. For example, on email chains that contained a (C) for confidential, Clinton told the FBI "she did not know what the '(C)' meant at the beginning of the paragraphs and speculated it was referencing paragraphs marked in alphabetical order."

Reince Priebus, the chairman of the Republican National Committee, characterized the FBI's investigative documents as "a devastating indictment of [Clinton's] judgment, honesty and basic competency."

During the course of the FBI's investigation, the bureau obtained "computer equipment" and "mobile devices" from Clinton, which included "equipment associated with two separate e-mail server systems used by Clinton."

The FBI "forensically reviewed the items to recover relevant evidence.... US Intelligence Community (USIC) agencies determined that 81 e-mail chains, which FBI investigation determined were transmitted and stored on Clinton's UNCLASSIFIED personal server systems, contained classified information ranging from the CONFIDENTIAL to TOP SECRET/SPECIAL ACCESS PROGRAM levels at the time they were sent between 2009-2013."

Additionally, "the FBI investigation determined Clinton contributed to discussions in four e-mail chains classified as CONFIDENTIAL, three e-mail chains classified as SECRET/NOFORN [not to be shared with foreign nationals], and four e-mail chains classified as TOP SECRET/SAP. Investigation identified 67 instances where Clinton forwarded e-mails to either State personnel or [redacted] for printing that were identified as classified CONFIDENTIAL or SECRET through either the State FOIA process or FBI classification determination requests."

Top Secret/SAP, or special access program, is a classified designation "deemed so sensitive that it requires more rigorous protection than other classified information," said Steven Aftergood, a classification expert and the director of the Project on Government Secrecy at the Federation of American Scientists.

The Obama administration's targeted killing program would likely be classified Top Secret/SAP.

Clinton told the FBI she did not believe any of the emails later determined to be a SAP contained classified information. She also said she could not recall "any specific briefing on how to handle SAP information" but she was aware that it needed to be handled "carefully."

The FBI's memorandum said that dozens of emails Clinton received from her unofficial adviser and close confidante, Sidney Blumenthal, were determined to contain information at the confidential and secret level. The FBI interviewed Blumenthal last January about the source of the information he emailed to Clinton.

"According to Blumenthal, the content of the memos, which addressed topics to include Benghazi and foreign political developments, was provided to him from a number of different sources to include former USIC [United States Intelligence Community] employees and contacts, as well as contacts within foreign governments," the FBI's partially redacted memorandum said.

As VICE News first reported in July, the FBI's yearlong probe stemmed from a so-called "Section 811" referral from the Intelligence Community's Inspector General (ICIG). The ICIG determined that classified, national security information in Clinton's emails may have been "compromised" and shared with "a foreign power or an agent of a foreign power."

Moreover, Clinton exchanged 22 emails in 2011 and 2012 that the State Department determined were top secret. She exchanged them with three aides: her deputy chief of staff, Jacob Sullivan, her chief of staff, Cheryl Mills, and Deputy Secretary of State William Burns. A majority of the top secret emails are email chains between Sullivan and Clinton.

The FBI's memorandum said agents "interviewed multiple officials who authored and/or contributed to e-mails, the content of which has since been determined to contain classified information. [US government] employees responsible for initiating classified e-mail chains included State Civil Service employees, Foreign Service employees, Senior Executive Service employees, Presidential appointees, and non-State elected officials."

The FBI said Clinton "did not recall receiving any e-mails she thought should not have been on an unclassified system."

"She relied on State officials to use their judgment when e-mailing her and could not recall anyone raising concerns with her regarding the sensitivity of the information she received at her e-mail address," the FBI's memorandum said. "The FBI provided Clinton with copies of her classified e-mails ranging from CONFIDENTIAL to TOP SECRET/SAP and Clinton said she did not believe the e-mails contained classified information."

Clinton's email practices have taken a notable toll on her campaign and her trustworthiness in the eyes of voters. For more than a year, she has insisted she never sent or received any emails from her private server that contained classified information. The FBI's documents reveal that tens of thousands of Clinton's emails were deleted after the New York Times first disclosed on March 2, 2015 that she had exclusively used private email to conduct official business during her tenure as Secretary of State. The FBI has since recovered more than 15,000 of the deleted emails.

After the FBI wrapped up its investigation last July, it recommended to the Department of Justice that neither Clinton nor any of her aides should face charges. In an extraordinary news conference, FBI director James Comey said that while the FBI "did not find clear evidence that Secretary Clinton or her colleagues intended to violate laws governing the handling of the classified information, there is evidence that they were extremely careless in their handling of very sensitive, highly classified information."

The State Department said it would reopen an internal review. Even though Clinton and her aides no longer work at the State Department, they could still be subject to a number of penalties, such as losing their security clearances.