Candidate's use of unauthorised private email server has long been under scrutiny
The FBI has opened a new investigation into Hillary Clinton's personal emails following the discovery of additional messages which "appear to be pertinent".
FBI director James Comey said the probe will examine whether the new emails - connected to an "unrelated case" - contain sensitive government information.
Here is a timeline of the email scandal that has dogged the Democratic presidential candidate's campaign:
:: 13 January, 2009 - The internet domain clintonemail.com is registered, operating from a private server based in New York.
:: 21 January, 2009 - Hillary Clinton is sworn is as US Secretary of State.
:: 1 February, 2013 - Mrs Clinton's tenure as Secretary of State comes to an end.
:: 3 March, 2013 - Gawker publishes the email address - email@example.com - after a hacker known as "Guccifer" revealed it after the email account of former Bill Clinton aide Sidney Blumenthal was compromised.
:: November, 2014 - The House Select Committee investigating the 2012 attack on the US Embassy in Benghazi, Libya, requests emails from Mrs Clinton. Some 300 emails from the private account are delivered to the committee.
:: December, 2014: Mrs Clinton's office delivered around 55,000 pages - some 30,490 emails - to the State Department. Another 31,830 emails from her tenure were deemed private and not delivered.
:: 3 March, 2015: The New York Times reveals that Mrs Clinton used a private email server while she was US Secretary of State.
:: 5 March, 2015: Mrs Clinton writes on Twitter that she asked the State Department to release her messages.
:: 10 March, 2015: She speaks publicly about the email server for the first time, saying she used the private account because it was more convenient than maintaining separate personal and office addresses.
:: 22 May, 2015: The first batch of emails relating to the Benghazi attacks are released.
:: 27 May, 2015: A federal judge orders the State Department to release batches of the emails around every 30 days.
:: 25 June, 2015: The State Department reveals it is missing 15 work-related emails between Mrs Clinton and Mr Blumenthal. The emails were uncovered by the committee examining the Benghazi attacks, but were not included in the records submitted to the State Department.
:: 29 June, 2015: Two inspectors general determine that Mrs Clinton's private account contains "hundreds of potentially classified emails".
:: 23 July, 2015: It is revealed that the FBI was informed about the potential loss or mishandling of classified information by the inspectors general. The FBI says Mrs Clinton is not a target, but that the inspectors general concluded that information classified at the time it was sent was transmitted on Mrs Clinton's server.
:: 18 August, 2015: Mrs Clinton responds to questions by reporters on the campaign trail about where she wiped her server with: "what, like with a cloth or something?"
:: 19 August, 2015: Mrs Clinton's campaign acknowledged there was material on the server that was later classified. A spokesman says she was a "passive recipient of unwitting information that subsequently became deemed as classified".
:: 8 September, 2015: Mrs Clinton apologises for using a private email server in an ABC News interview.
:: 10 September, 2015: The IT staffer paid to maintain the server invokes his constitutional right not to incriminate himself in front of a House of Congress panel.
:: 22 October, 2015: Mrs Clinton testifies before the House Benghazi Committee. She repeats that she did not send information marked classified at the time.
:: February, 2016: A federal judge orders the remainder of the emails to be released by 29 February.
:: 23 February, 2016: Conservative watchdog Judicial Watch is granted the right to gather evidence in a lawsuit against the State Department about the use of the email server. The lawsuit means Mrs Clinton and her aides may be called to testify.
:: 29 February, 2016: The State Department finishes releasing the final batch of emails.
:: 25 May, 2016: The State Department's Inspector General releases a report that is critical of Mrs Clinton's use of a private email server. It stresses that private email was not forbidden by law, but that it was clear department policy that employees should use government systems for work.
:: 28 June, 2016: Attorney General Loretta Lynch met privately with former President Bill Clinton in Arizona. Ms Lynch says they did not discuss the investigation.
:: 2 July, 2016: Mrs Clinton is interviewed by the FBI for three-and-a-half hours.
:: 5 July, 2016: FBI Director James Comey says Mrs Clinton was "extremely careless" in handling classified information while Secretary of State and said scores of emails on her server contained highly classified information. But he says the FBI will not recommend criminal charges.
:: 28 October, 2016: The FBI reveals it is opening a new investigation into the email server after the discovery of new emails in an "unrelated case".