A thumb drive and a server containing copies of emails Hillary Clinton sent and received while US secretary of state will be handed over to the FBI, media reports said on Tuesday.

Clinton has been criticized for her decision to use a personal e-mail server while serving as secretary of state, and the Federal Bureau of Investigation has recently begun looking into the possibility that Clinton sent and received classified information from the server.

"It is her hope that State and the other agencies involved in the review process will sort out as quickly as possible which emails are appropriate to release to the public, and that the release will be as timely and transparent as possible," Clinton campaign spokesman Nick Merrill told CBS News.