BAIJI, Iraq -- U.S. soldiers emerged into sunlight after exploring one of Saddam Hussein's most elaborate tunnel complexes Sunday, bewildered by a single question: Why did the Iraqi leader build an entire oil refinery inside a mountain?
Blueprints scattered on the floor of a dusty office in the complex indicate construction started in December 1980, three months after the start of the Iraq-Iran war. But whether the refinery was encased in rock for security or other reasons wasn't immediately clear to soldiers of the 4th Infantry Division.
"Maybe it was Saddam's personal gas plant. I don't know what it is," said Maj. Edward Chesney, 40, operations officer for the 3rd Battalion, 66th Armored Regiment, who oversaw infantry searching room after room of the complex by flashlight.
Invisible from the main highway, the refinery's entrance is reached by an access road running through a Special Republican Guard camp. The entrance is pocked by shrapnel from American bombs from the 1991 Gulf War -- one of which sits unexploded and rusting outside -- but inside, the thick, reinforced concrete ceilings of the complex show no damage.
"The ultimate bunker is a mountain," said Lt. Col. Larry Jackson, 42, of Abbeville, S.C., commander of the 3-66th, which is responsible for the Baiji area.
Although Baiji, 120 miles north of Baghdad, has a population of only 15,000, many of Iraq's most important facilities were located in or near the city. Its central location between Mosul, Kirkuk and Baghdad made it geographically significant. The proximity to Saddam's hometown of Tikrit provided a loyal work force.
The area also has an aboveground refinery and a rocket fuel production facility. On the outskirts, a 12-square-mile camp, now abandoned, holds several million tons of ammunition.
"It's a hub of industry here. It supports a whole lot of stuff from Baghdad to Kirkuk, but why the Iraqis put (a refinery) here, your guess is as good as mine," Jackson said.
The refinery was the latest of Saddam's underground complexes that U.S.-led coalition forces have discovered as they move across Iraq.
Australian troops found a vast network of underground bunkers at a major air base captured in western Iraq in the final days of the war. In early April at the airport outside Baghdad, soldiers from the U.S. Army's 101st Airborne Division searched a 12-room complex inside a cave with white marble floors, 10-foot ceilings and fluorescent lighting. They found signs of recent abandonment -- but no Iraqis.
The underground oil refinery looked like it had been abandoned for some time. A thick layer of dust covered everything.
After returning to base camp, Capt. Tad Corkery, a spotter with the 4th Battalion, 42nd Field Artillery Regiment, shrugged and said only Saddam could know what it was all for.
"Guess we have to find him and ask him," said the 28-year-old from Andover, Mass.
Key Iraq developments
With shovels and their bare hands, Iraqis excavated a mass grave filled with the remains of dozens of people who witnesses said were executed after a 1991 Shiite uprising.
Police in Iraq's capital returned to work in force, but there were few patrols on Baghdad's lawless streets as officers struggled to navigate a chaotic new order.
Defense Secretary Donald H. Rumsfeld said the United States will have to rely on low-ranking Iraqi officials from Saddam Hussein's government to disclose the existence of banned weapons.
Rumsfeld also said it is "an open question" as to how many U.S. troops will remain in Iraq and how long they will serve.
The American civilian overseeing Iraq's reconstruction discussed the country's future Sunday exile and autonomous Iraqi enclaves to help create a new government.
Iraq's American administrators have appointed two Iraqi oil officials and a retired American oil executive to head Iraq's Oil Ministry, according to a spokesman.
A U.S. soldier died of a gunshot wound after an apparent accident involving his own weapon in Iraq, a U.S. Central Command statement said.
President Bush is considering a stopover in the Polish city of Krakow en route to Russia this month to thank Poles for participating in the Iraq war, Polish President Aleksander Kwasniewski said.