Mon Mar 1, 5:44 AM ET BAGHDAD, Iraq - A large explosion was heard Monday in central Baghdad and appeared to have come from the vicinity of the headquarters of the U.S. occupation authority.
Shortly after the blast, a Black Hawk helicopter circled over the green zone, the U.S. compound that includes Saddam Hussein (news - web sites)'s former Republican Palace and serves as headquarters of the U.S.-led coalition.
There were no immediate details on the cause of the blast