Democratic presidential candidate Hillary Clinton in Cleveland, Ohio. Jeff Swensen/Getty Images An aide to former President Bill Clinton destroyed two of Hillary Clinton's phones by using physical force, according to documents released by the FBI on Friday.

The FBI said in a report that the aide, Justin Cooper, recalled "two instances where he destroyed Clinton's old mobile phones by breaking them in half or hitting them with a hammer."

Clinton used a number of phones while serving as secretary of state. The FBI said it identified 13 mobile devices used to possibly send emails using Clinton's private email server.

Huma Abedin, a top aide to Clinton, told the FBI that Clinton was known to use a new phone for a few days and then switch back to an older model that she understood how to use better.

When this would happen, aides would help transfer her SIM cards. The FBI report said that "the whereabouts of Clinton's devices would frequently become unknown once she transitioned to a new device."

The Clinton campaign released a statement Friday saying it was "pleased" the FBI released documents related to the email probe.