Baghdad, Dec 24, SPA -- The U.S. military opened a probeFriday into a deadly blast at an army base in northern Iraqthat killed 22 people, trying to determine how a suicidebomber managed to enter the heavily fortified facility. An investigation team, led by Brig. Gen. Richard P.Formica, started its work in Mosul as U.S. DefenseSecretary Donald H. Rumsfeld paid a surprise visit to the wounded soldiers at the base. "The main person in charge of the investigation arrivedlast night and he's starting his investigation today," Lt.Col. Paul Hastings said, a U.S. spokesman in the Mosul basesaid. "Now we have a pretty good idea that it was a suicidebomber," Hastings said. "He (Formica) is going toinvestigate into the how's _ how did that happen?" "The investigation will be conducted quickly andthoroughly," Hastings added, however, there is no deadlineset for the conclusions to come out.--SPA1522 Local Time 1222 GMT www.spa.gov.sa/227235