Hillary Clinton's presidential campaign hailed the announcement by FBI Director James Comey that his department would not recommend criminal charges against her after an investigation into her use of a private email server during her time as secretary of state.

"We are pleased that the career officials handling this case have determined that no further action by the department is appropriate," said Clinton spokesman Brian Fallon. "As the secretary has long said, it was a mistake to use her personal email and she would not do it again.

"We are glad that this matter is now resolved," he added.

Fallon largely ignored Comey's criticism of Clinton's handling of classified material in her email as a result of the email arrangement and instead focused on the now-diminished likelihood that she would face charges.

In his 15-minute statement, Comey said that Clinton and her aides were "extremely careless" in their handling of sensitive information. He announced that 110 emails in the group of 30,000 emails that had been turned over to the State Department contained classified information, including eight email chains that contained top secret information.

As Comey spoke, Clinton was across town in D.C., delivering remarks at a convention of the National Education Association, the largest teachers union and one of Clinton's earliest and biggest backers. They spoke simultaneously, and Clinton did not address Comey's comments.