By Daniel Strauss and Jordy Yager - 05/14/13 06:26 PM EDT
He said because he recused himself early in the investigation, he did not have all the facts surrounding the investigation.
"I don't know all that went into the formulation of the subpoena," Holder said at a press conference on Tuesday.
Holder, however, did say the leak that sparked the subpoena was "a very serious leak."
Read more on The Hill's Blog Briefing Room.