Hillary Clinton created a previously undisclosed email account to communicate when her private server system was down, documents made public by the FBI Friday show.

Monica Hanley, a former Clinton aide, told FBI investigators that Clinton likely created the second private account — a "gmail.com" address — to send messages when her server crashed in 2011 during a trip to Croatia.

An FBI report made public earlier this month showed Clinton and her staff had been warned repeatedly about using private accounts while overseas. What's more, Clinton and her staff have repeatedly said the former secretary of state used just one personal address.

The 189 new pages of notes from the FBI's closed investigative file came amid controversy over the five immunity agreements doled out to witnesses in the criminal probe.