U.S. commanders are re-examining security procedures for every American base in the country, trying to figure out how a bomber got into their midst, reports CBS News Correspondent Kimberly Dozier.
They are also hinting there are some major operations in the offing aimed at the enemies who cost so many American lives this week. In the triangle of death south of Baghdad, U.S. troops have already carried out several operations, arresting 44 suspects Wednesday.
Myers, chairman of the Joint Chiefs of Staff, isn't saying whether authorities think the bomber worked at the base, or breached security.
But military investigators reportedly suspect that the bomber might have been an Iraqi worker who is now unaccounted for.
FBI investigators believe they have found the remains of a suicide bomber's torso and a harness device within the mess tent wreckage.
Baghdad-based FBI bomb technicians are helping to identify the type of explosive and components used, which could provide forensic links to previous Iraq bombings.
In other recent developments:
Tuesday's explosion in Mosul ripped through a dining hall tent while hundreds of troops were sitting down to lunch at Forward Operating Base Marez near the northern city of Mosul. Of the 22 people killed, 14 were U.S. military, 4 U.S. civilian contractors, three Iraqi security force members and one other non-U.S. individual.
Of the 69 wounded, 25 will return to duty, Myers said. The majority of the wounded in the attack are being treated at Landstuhl hospital in Germany. Landstuhl is where troops who need the kind of medical attention that is difficult to give in Iraq are brought. Seventeen soldiers are in the intensive care unit there in critical condition, reports CBS News Correspondent Sheila MacVicar.
Doctors at the hospital say that because the troops were at lunch and not wearing battle armor, they are treating more critical wounds to the torso than usual. Most of the injuries they treat are to the extremities.
The militant group Ansar Al Sunna claims one of its operatives carried out the attack.
Tuesday's attack would not be the first incident of insurgent infiltration: two rebels infiltrated the heavily guarded Green Zone in downtown Baghdad in October, setting off two bombs that killed 10 people.
Although officials say infiltration by insurgents is a concern, troops fears of both spy infiltration and physical harm are not likely to be alleviated anytime soon, reports CBS News' David Martin. Tens of thousands of Iraqis work for the American military as laborers, soldiers and policemen. They have proved an integral part of U.S. strategy for rebuilding the country.
Despite the attack and other violence elsewhere in Iraq, Defense Secretary Donald Rumsfeld and Myers said the U.S.-led forces are winning the battle against the insurgents, and in the process protecting America from another terrorist attack. Rumsfeld said terrorists would have "a deep pool from which to draw recruits and attack" across the globe if the United States fails in Iraq.
"Freedom is at stake in Iraq and is achievable," Rumsfeld said. "The only mistake would be to go back to darkness in Iraq."
While offering condolences to relatives of those killed, Rumsfeld lashed out at critics who accuse the Pentagon of failing to provide enough protective equipment and facilities for U.S. forces.
Rumsfeld said he stays awake at night worrying about the troops. "I am truly saddened by the thought that anyone could have the impression that I, or others here, are doing anything other than working urgently to see that the lives of the fighting men and women are protected and are cared for in every way humanly possible."