The State Department’s Office of Inspector General is investigating the special internal panel that probed the Benghazi terror attack for the State Department, Fox News has confirmed.

The IG’s office is said by well-placed sources to be seeking to determine whether the Accountability Review Board, or ARB — led by former U.N. Ambassador Thomas Pickering and former Chairman of the Joint Chiefs of Staff Adm. Mike Mullen — failed to interview key witnesses who had asked to provide their accounts of the Benghazi attacks to the panel.

The IG’s office notified the department of the “special review” on March 28, according to Doug Welty, the congressional and public affairs officer of the IG’s office.