Hillary Clinton once left classified documents behind in a Russian hotel.

The US Federal Bureau of Investigation (FBI) yesterday released further evidence showing that Clinton demonstrated "extreme carelessness" in handling classified information.

Presidential candidate Hillary Clinton. Photo: AP

During a trip to Russia as U.S. Secretary of State, Clinton and her assistants left behind a classified document when they left their hotel room. Fortunately, a U.S. diplomatic security officer discovered it, ABC News reported, citing the FBI.

The agency argues that Clinton's assistant should not have brought the briefcase into the hotel in the first place. This is part of nearly 200 pages of new FBI documents related to the investigation into Democratic presidential candidate Clinton's use of a personal email account.

FBI Director James Comey affirmed that although investigators found no evidence that Clinton knew classified information was being transferred to a server at her home, the agency concluded that Hillary was "extremely careless" in handling classified information.

New FBI documents have been released to further explain why FBI officials decided not to charge Clinton and her aides.

In early July, the US Attorney General accepted the FBI's recommendation not to prosecute and to close the investigation into Hillary Clinton's use of a personal email server while she was Secretary of State.

According to VNE