WASHINGTON, Feb. 6 — A House committee report on Tuesday questioned whether some of the billions of dollars in cash shipped to Iraq after the American invasion — mostly in huge, shrink-wrapped stacks of $100 bills — might have ended up with the insurgent groups now battling American troops.

The report was released by the House Oversight and Government Reform Committee at a hearing when Democrats sharply questioned the former American civilian administrator in Iraq, L. Paul Bremer III, about lax management of the nearly $12 billion in cash shipped to Iraq between May 2003 and June 2004.

Mr. Bremer defended his performance as head of the Coalition Provisional Authority in Iraq, noting that the United States had to bring tons of American dollars into Iraq because the country had no functioning banking system.

“We had to pay Iraqis in cash,” Mr. Bremer said of the money, most of which came from Iraqi oil sales. “Delay would have been demoralizing and unfair to millions of Iraqi families.”