FBI director Mueller says the bureau is assisting the Pentagon in the WikiLeaks probe

FBI Director Robert Mueller says the bureau is assisting the Defense Department in its criminal investigation into the release of some 91,000 secret U.S. military documents on Afghanistan.

Mueller made the comment on Capitol Hill as the editor-in-chief of WikiLeaks claimed that his organization, which released the material, doesn't know who provided the secret documents.

The FBI director told the Senate Judiciary Committee that the bureau cannot say where the investigation will lead.