Baghdad, Iraq ? U.S. troops sweeping through Fallujah on Thursday found what appeared to be a command center used by followers of Jordanian terrorist Abu Musab al-Zarqawi, and a U.S. general expressed confidence the battle for the city has “broken the back of the insurgency.”

A separate raid near the suspected command center uncovered a bomb-making workshop where an SUV registered in Texas was being converted into a car bomb and a classroom that held flight plans and instructions on shooting down planes, according to a CNN crew embedded with the U.S. Army.

Gunbattles still flared in Fallujah as troops hunted holdout insurgents five days after the military said its forces had occupied the entire city 40 miles west of Baghdad. One U.S. Marine and one Iraqi soldier were killed, U.S. officials said.

At a base outside Fallujah, Lt. Gen. John Sattler, commander of the 1st Marine Expeditionary Force, said the U.S. casualty toll in the Fallujah offensive stood at 51 dead and about 425 wounded. An estimated 1,200 insurgents have been killed, with about 1,025 enemy fighters detained, the military says.

Sattler told reporters he felt the U.S.-led attack on the city had dealt a serious blow to the insurgency.

“We feel right now that we have, as I mentioned, broken the back of the insurgency. We’ve taken away this safe haven,” Sattler said, adding that insurgents had scattered elsewhere in Iraq where they lacked the resources available in their former stronghold.