WASHINGTON (AFP) -- The FBI on Friday poured fresh fuel on the fire sparked by Hillary Clinton's use of a private email server as secretary of state, releasing heavily redacted notes on its probe, which White House rival Donald Trump seized on to attack her fitness for office.
The 58 pages -- 14 of which were entirely blacked out -- showed that the FBI found no evidence her email system was compromised but decided it could not be ruled out because some of her mobile devices were not recovered.
"The FBI did find that hostile foreign actors successfully gained access to the personal email accounts of individuals with whom Clinton was in regular contact and, in doing so, obtained emails sent to or received by Clinton on her personal account," the notes said.
Clinton's use of a private server has been the subject of simmering controversy as she runs for president against Trump, the Republican candidate.
The documents' release follows the FBI's recommendation in July not to prosecute Clinton for sending unsecured emails with classified material through the server, though it found her to have been "extremely careless."
Clinton's campaign said it was "pleased" with the report's release.
"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," it said in a statement.
But Trump's campaign pounced, charging that the notes "reinforce her tremendously bad judgment and dishonesty.
"Clinton's secret email server was an end run around government transparency laws that wound up jeopardizing our national security and sensitive diplomatic efforts," Trump spokesman Jason Miller said in a statement.
Trump said Clinton's answers to the FBI "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," he said in a statement.
Embarrassing revelations include a passage in the report in which the 68-year-old Clinton told investigators she was unaware that confidential material was marked with a "C."
"Clinton stated she did not know what the '(C)' meant at the beginning of the paragraphs and speculated it was referencing paragraphs marked in alphabetical order," the report said.
"When asked of her knowledge regarding TOP SECRET, SECRET, and CONFIDENTIAL classification levels... Clinton responded that she did not pay attention to the 'level' of classification and took all classified information seriously," it added.
The report also revealed that Colin Powell, who served as secretary of state from 2001 to 2005, warned Clinton to "be very careful" regarding emails.
"Powell warned Clinton that if it became 'public' that Clinton had a BlackBerry, and she used it to 'do business,' her emails could become 'official record(s) and subject to the law,'" the report said, noting Clinton had emailed Powell after taking office in 2009 to ask about his use of a BlackBerry.
"Powell further advised Clinton, 'Be very careful. I got around it all by not saying much and not using systems that captured the data.'"
The FBI notes said investigators identified 13 mobile devices that "potentially were used to send emails using Clinton's Clintonemail.com email address."
It said eight of the devices were BlackBerries that she used while secretary of state, and the other five were devices, including BlackBerries, that she used after leaving office.
In its summary of the interview with Clinton, the agency said she had received no direction on preserving or producing State Department records while transitioning out of her post.
However, Clinton noted that she had suffered a concussion in December 2012, less than two months before leaving office, and then had 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 summary said.
The apparent suggestion that Clinton's blood clot led to memory loss could be potent fodder for the Trump camp -- as it seeks to portray the Democrat as lacking the stamina for the job.
Clinton's campaign spokesman Brian Fallon sought to cut short any such notion, tweeting: "Asked abt briefings in late '12, Clinton said 2 things: (1) she couldn't recall each briefing (2) she missed part of that time due to health."
Of some 30,000 emails Clinton subsequently turned over to the FBI, the agency's director James Comey has said 110 contained classified information. Clinton had said none was classified at the time they were sent.
Meanwhile, the State Department has been ordered to review for possible release nearly 15,000 additional emails and documents uncovered during the FBI investigation that had not been disclosed by her lawyers.