When exactly the referral was made to the US attorney's office was not immediately clear, and prosecutors there may decline to prosecute.

Last week, the IG issued a report finding that McCabe "lacked candor" on four occasions with internal investigators when discussing a Wall Street Journal article about the FBI's Clinton Foundation investigation, according to a copy of the report obtained by CNN.

In addition, the inspector general determined that McCabe was not authorized to disclose the existence of the investigation because it was not within the department's "public interest" exception for disclosing ongoing investigations.

The disclosure to the Journal was made "in a manner designed to advance his personal interests at the expense of department leadership," the report said.