A day after Vice President Joe Biden and his wife, Dr. Jill Biden, landed in Iraq, a loud blast shook the U.S. embassy compound in Baghdad. “There was a small explosion in the International Zone,” said a U.S. official. “The incident is being investigated. There were no injuries or property damage.” An aide assured media that the Bidens are “safe and unharmed.” As at least five mortar rounds fell in what was formerly known as the Green Zone, according to Iraqi police, as sirens rang and a loudspeaker blasted: "Duck and cover. Get away from the window. Take cover and await further instructions.” Biden’s holiday weekend trip to Iraq was unannounced until he arrived yesterday, when officials said he was on a mission to assess the state of the country leading up to Obama’s planned end to the U.S. "combat mission" in Iraq at the end of August. He was also tasked with encouraging Iraqi leaders to break the four-month stalemate that has followed March’s parliamentary elections.