The FBI Sept. 2 published a detailed report on its investigation into Democratic presidential candidate Hillary Clinton’s use of a private email server while she was secretary of state. (Sarah Parnass/The Washington Post)

Secretary of State Hillary Clinton and her staffers employed an informal and sometimes haphazard system for exchanging and storing sensitive information and were at times either unaware or unconcerned with State Department policy, documents from an FBI investigation into her private email server system show.

The documents reveal a myriad of new details about the email set-up and show that investigators found multiple attempts by hackers to access Clinton’s system — a series of personal devices and servers that the Democratic presidential candidate told investigators she used as a matter of convenience while she was secretary of state.

The materials, which include a summary of the FBI’s entire investigation as well as Clinton’s hours-long interview with agents in July, contain no major revelations. But they offer new details that Clinton’s political opponents will be able use in the months leading up to the November election. The summary shows that Clinton’s account to law enforcement was generally consistent with what she has said about her email situation publicly, but she repeatedly told agents she could not recall important details or specific emails she was questioned about.

Clinton has been dogged by questions about her use of the private email server since the start of her presidential campaign and her Republican opponent, Donald Trump, has used the issue to argue she is untrustworthy.

FBI Director James Comey said on July 5 that Hillary Clinton should not be charged for her use of a private email server during her time as secretary of state. Here's what he said, in three minutes. (Peter Stevenson/The Washington Post)

Clinton campaign spokesman Brian Fallon said, “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.”

Trump said in a statement: “Hillary Clinton’s answers to the FBI about her private email server 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.”

FBI Director James B. Comey announced in July that his agency would not recommend criminal charges against Clinton for her use of a private email server, though he said at the time she and her staffers were “extremely careless” in how they treated classified information. He said the decision was based largely on the fact that investigators did not find Clinton intended to mishandle classified material, though such material did traverse her private server.

Ordinarily internal documents from FBI investigations are not made public. However, Comey has said the unusually high profile case warranted more robust public disclosures than is standard.

The FBI found no evidence that anyone penetrated the email of the former secretary of state herself — although “hostile foreign actors successfully gained access to the personal e-mail accounts of individuals with whom Clinton was in regular contact and, in doing so, obtained e-mails sent to or received by Clinton on her personal account,” the bureau wrote. Those include confidante Sidney Blumenthal, whose emails were hacked and publicly revealed by Romanian hacker Marcel Lehel Lazar.

The bureau wrote in its report that it was unable to track down all of Clinton’s electronic equipment because it had been destroyed or lost. One staffer told investigators he destroyed two mobile devices “by breaking them in half or hitting them with a hammer.” The FBI said it requested 13 devices from the law firm representing Clinton, and the firm said it could not produce any.

The FBI wrote that “investigative limitations, including the FBI’s inability to obtain all mobile devices and various computer components associated with Clinton’s personal e-mail systems, prevented the FBI from conclusively determining whether the classified information transmitted and stored on Clinton’s personal server systems was compromised via cyber intrusion or other means.”

Clinton told the FBI that she used the private server for convenience, not to evade public record laws. But the documents show that former secretary of state Colin Powell appeared to advise her early in her term that private email could give her more control over her communications in the face of public inquiries.

In January 2009, according to the FBI, Clinton contacted Powell, who also used a personal email account during his time in office, to ask about his use of a BlackBerry. According to the FBI, Powell “warned Clinton that if it became ‘public’ that Clinton had a BlackBerry, and she used it to ‘do business,’ her e-mails could become ‘official record[s] and subject to the law.’”

“Be very careful,” Powell advised Clinton, according to the FBI. “I got around it all by not saying much and not using systems that captured the data.”

Clinton told investigators she understood Powell’s comments to mean any work-related communications would be government records, and they did not factor into her decision to use a personal email. She indicated that she believed her own records were being preserved when she emailed other State Department officials at their government addresses.

Powell said he could not recall the details of the years-old exchange, though he said he used his email system “openly for unclassified communication” and “saw no need for, say, an email to one of my kids or a friend becoming an official record.”

The FBI’s report traced the history of Clinton’s private server use, detailing ad hoc efforts to backup data and respond to requests for records. In one instance, after Clinton left office, someone created a personal Gmail account to move an archive of Clinton’s email on a laptop to a server run by Platte River Networks, a company Clinton had hired. The person then attempted to ship the laptop back to another person connected to Clinton.

According the FBI report, the laptop, which had not been wiped, got lost in transit. And the FBI would come to find on the Gmail account dozens of classified emails.

Someone, apparently at Platte River, did delete Clinton emails in late March 2015 in what the person described as an “oh s---” moment, having been instructed months earlier to permanently destroy the emails of two Clinton aides and change how long emails were retained.

That person, whose name is redacted, had received a request from the House Committee on Benghazi to preserve emails on March 9. Clinton told investigators she was unaware of the deletions. Andy Boian, a spokesman for Platte River, declined to comment.

Clinton told FBI agents that she did not know much about how the government classified information. For instance, she said she did not pay attention to the difference between levels of classification, like “top secret” and “secret,” indicating she took “all classified information seriously.” When shown an email she received in which a paragraph had been marked with a “C,” a standard way of indicating it included “confidential” information, Clinton at first speculated to agents that the marking was indicating that email contained bullet points in alphabetical order.

Clinton indicated she never sought nor received permission to use a private server and said she largely turned over the set-up of the system to aides.She said she could not remember a cable that was sent to all State Department employees under name in June 2011, advising her employees not use to private email for work. She said that all cables of a “certain policy nature” went out under her name.

Clinton told agents that she generally received classified material in personal briefings or on paper, which she read in specially prepared secure facilities, and that she didn’t remember ever receiving an email that she thought shouldn’t be sent through the unclassified system. The FBI’s report says Clinton took her BlackBerry into a State Diplomatic Security post where other State Department personnel were not allowed to carry mobile devices, though a Clinton aide said Clinton left the secure area before using it.

Much of Clinton’s interview, which is described in an 11-page summary, appears to have consisted of FBI agents showing Clinton specific email exchanges that they determined included classified content and asking her to comment.

Repeatedly, Clinton said she could not remember the specific exchange but had trusted at the time that her staff at the State Department knew how to handle classified material and would not email her material they should not. The exact nature of those classified emails are redacted in the version of the summary released by the FBI but it is clear they included deliberations on drone targets. Shown one July 2012 email she exchanged with President Obama at his own highly secure address, Clinton indicated that she recalled sending the note on an airplane during a trip to Russia.

Clinton also told the FBI that she played no role in sorting her work and personal emails after she left office other than to instruct her legal team to submit to the State Department all those emails that were “work-related or arguably work related.” Comey has indicated the FBI discovered thousands of work related emails that Clinton had not turned over but said the agency found no effort to purposely delete or conceal emails.