U.S. Marines have found beheading chambers, bomb-making factories and even one Iraqi hostage as they swept through Fallujah (search) — turning up hard evidence of the city's role in the insurgent campaign to drive American forces from Iraq (search).

Marines on Sunday showed off what they called a bomb-making factory, where insurgents prepared roadside explosives and car bombs that have killed hundreds of Iraqi civilians and U.S. troops.

Wires, cell phones, Motorola handheld radios and a Plastic foam box packed with C4 (search) plastic explosives sat in the dark building down an alley, along with three balaclava-style masks reading: "There is only one god, Allah, and Muhammad is his messenger."

"It's all significant because this is not the kind of stuff an average household has," said Lt. Kevin Kimner, 25, of Cincinnati assigned to the 3rd Battalion, 5th Marines. "This is better than Radio Shack."

So far U.S. troops have only found two hostages, one Iraqi and one Syrian. Marines last week found the Iraqi in a room with a black banner bearing the logo of one of Iraq's extremist groups. He was chained to the wall, shackled hand and foot in front of a video camera. The floor was covered with blood.

The rescued Syrian was the driver for two French journalists, Christian Chesnot and Georges Malbrunot, missing since August. The journalists have not been found, but France maintains they are still alive.

A Marine officer said he found signs that at least one foreign hostage was beheaded in that room. The Marine, who spoke on condition of anonymity, did not give details.

The Iraqi hostage, who had been beaten on the back with steel cables, said his tormentors were Syrian and that he thought he was in Syria until the Marines found him, the Marine said. Other militants came and went, but "The Syrians were always in charge," the Marine said.

The hostage was in a room — inside a compound that also had AK-47 rifles, improvised bombs, fake identification cards and shoulder-fired missiles that could down an airliner. Beneath it were tunnels running under the northern Jolan neighborhood.

Marines said weapons depots were strategically placed throughout Jolan. Insurgents marked many of the caches with a piece of brick or rock, suspended from the buildings by a piece of string or wire.

U.S. officials hope that by retaking Fallujah they can deprive the rebels of an important headquarters and boost security in Iraq ahead of elections scheduled for January.

Among the rebels' most-fearsome weapons have been the car bombs and roadside explosives that have targeted military convoys but also churches and other areas where civilians gather.

On Sunday, a hollowed-out plastic foam container about the size of two shoe boxes lay in the bomb lab, packed with plastic explosives and wires. The plastic foam box was covered in cloth to disguise it as an innocuous package.

Scattered on the ground nearby — cell phones, walkie-talkies, Motorola handheld radios — all used as detonators lay tangled in coils of wire. There was a computer without a hard drive and a box full of professional explosives-triggering.

"We've seen better," Kimner said of the detonators. "But they're reliable and they do the job right."

When Marines uncovered the lab in a Saturday sweep. Among the clutter were two wills, addressed to friends and family in Algeria.

"I will join my friends in heaven," the will read. "Don't cry for me. Celebrate my death."