Just weeks after news broke in March 2015 that Hillary Clinton had kept a private e-mail account while she was secretary of state, one of the employees who managed her private server deleted an archive of her e-mails, according to new FBI files released Friday.

Another aide told investigators that he destroyed some of her mobile devices, either by breaking them in half or hitting them with a hammer.

The portrait that emerges from 58 pages of FBI documents that were released Friday is one of secrecy, in which aides and advisers sought to prevent unfettered access to the correspondence Clinton had during her four years as the nation’s chief diplomat.

The documents also provide a rare peek into a sensitive and high level investigation into a political candidate. The FBI announced on July 5 that it would not recommend that any charges be brought against Clinton, though in an unusual public rebuke, Director James B. Comey said she had been “extremely careless’’ with classified information.

Clinton told investigators that she was unaware that her aide had deleted the e-mails in 2015. The FBI files include other new details, offering a portrayal of a secretary of state who, after setting up a system to correspond outside of the State Department’s own technology, appeared unfamiliar with the government’s classification system.

“Clinton could not give an example of how the classification of a document was determined,’’ according to the FBI’s notes in the documents. “Rather she stated there was a process in place at State before her tenure, and she relied on career foreign service professionals to appropriately mark and handle classified information.’’

When questioned about what the “C’’ stood for in one document, she speculated that it was for marking paragraphs in alphabetical order. In the classification system — which includes “secret’’ as well as “top secret’’ — the letter “C’’ stands for “confidential.’’

During her interview with the FBI. Clinton “could not recall any briefing or training by State’’ about retaining federal records or handling classified information.

After the FBI files were released Friday, Republican presidential candidate Donald Trump said her responses to the FBI “defy belief.’’

“After reading these documents, I really don’t understand how she was able to get away from prosecution,’’ Trump said in a statement.

Brian Fallon, a spokesman for Clinton’s campaign, said the campaign is “pleased’’ the notes were released. “These materials make clear why the Justice Department believed there was no basis to move forward with this case,’’ Fallon said.

Clinton’s decision to use a private e-mail server has dogged her entire presidential campaign, and new information about it is likely to keep trickling out all the way up to the November election.

The State Department, under court order, released tens of thousands of her e-mails last year on a monthly schedule. More recently, two conservative groups, Citizens United and Judicial Watch, have received separate batches of State Department e-mails from their litigation, which has showed a connection between work at the Clinton Foundation and the Clinton State Department.

And now, the FBI investigation uncovered thousands of additional work-related e-mails that will be released in weeks to come.

Clinton has repeatedly stated that she set up a private server out of “convenience.’’

The FBI documents reveal that she had 13 mobile devices, as well as five iPads. Only three iPads were turned over to the agency for a review, while the rest could not be found by Clinton’s attorneys.

The notes showed that the FBI received inconsistent information about whether Clinton kept a computer in the secure parts of her New York and Washington homes. Bringing a computer into the secure room could pose a security risk.

Three top staff members, including Huma Abedin, told investigators that Clinton had computers in the so-called Sensitive Compartmented Information Facility in those homes. “Clinton stated to the FBI she did not have a computer of any kind in the SCIFs in her residences,’’ according to notes released by the FBI on Friday.

Friday’s release consisted ofnotes from the investigation ­— and much of it filled in details about developments already in the news.

Clinton had said that she consulted with former secretary of state Colin Powell about using a private account. Powell has disputed that he provided much guidance, saying in an interview with a People Magazine reporter that: “Her people have been trying to pin it on me.’’

However, in the documents, it appears that Powell did provide Clinton with insights about using a private e-mail account.

Powell told Clinton — evidently in an e-mail — that if it ever became public that she used a private e-mail address to “do business,’’ those messages would become “official record and subject to the law,’’ according to the report.

“Be very careful,’’ Powell warned Clinton. “I got around it all by not saying much and not using systems that captured the data.’’

Clinton told the FBI that Powell’s advice “did not factor into her decision to use a personal e-mail account.’’ And she did little to keep her account a secret. She said hundreds of people at the State Department were aware of her personal e-mail account.

The notes released Friday included an 11-page summary of Clinton’s 3½-hour interview with the FBI in July. Much of that interview appeared to be focused on the classified e-mails that were found on her private server.

Clinton repeatedly said she relied on the judgment of others when it came to e-mails sent to her, and assumed her staff or career foreign service officers wouldn’t use the private account for sensitive information.

The FBI determined that Clinton’s e-mail setup was “potentially vulnerable to compromise’’ in her first few months in office before additional security measures were installed on the server.

The investigators did not find evidence confirming that Clinton’s e-mail server systems were actually compromised.

But Clinton’s systems administrator Bryan Pagliano was aware of “many failed log-on attempts’’ to the private server system he set up.

They were alarming enough that in 2011 he sent a memo to top State Department staff warning them not to use their personal e-mails too much for work purposes because “some compromised home systems have been reconfigured by these actors to automatically forward copies of all composed e-mails to an undisclosed recipient.’’

The new details continued to fill out a portrait of Clinton as not particularly tech-savvy or eager to embrace new technology. When she was issued a new BlackBerry, for example, she would use it for a few days and then request to “switch it out for an older version with which she was more comfortable,’’ according to the report.

The new documents also show instances in which Clinton was communicating with President Obama.

One of those e-mails was sent from Russia. Clinton said she was given no guidance on how she should use the president’s e-mail.

Clinton told investigators she consulted with former secretary of state Colin Powell about using private e-mail. “I got around it all by not saying much and not using systems that captured the data,’’ he reportedly advised her.

Three top Clinton staff members, including Huma Abedin, told investigators that Clinton had computers in the secure rooms of her houses in Washington and New York. Clinton said she did not have computers in those rooms.

Annie Linskey can be reached at annie.linskey@globe.com. Follow her on Twitter @annielinskey.