Democratic vice presidential candidate Tim Kaine on Sunday defended Hillary Clinton against criticism over her handling of classified information as secretary of state, saying she was unaware of the sensitivity of some information she exchanged over email because it had been "improperly labeled."

In July, the Federal Bureau of Investigation rebuked Clinton, the Democratic presidential nominee, for her use of a private email server during her tenure as secretary of state from 2009 to 2013, saying she was "extremely careless" in her handling of classified information.

According to records released by the FBI on Friday, Clinton told the bureau's investigators in a July interview that she could not recall getting any briefings on how to handle classified information or comply with laws governing the preservation of federal records.