TUWAITHA, Iraq – On a dusty road, just outside of Baghdad, lies one of the great mysteries of the Iraq war.

Just off the road behind fences and berms sits the 23-acre complex of Tuwaitha, Iraq’s main nuclear facility. It’s now defunct, but it’s still a storage area for 3,000 barrels of low-grade uranium and other more dangerous radioactive materials.

The Bush administration claimed, contrary to reports by U.N. weapons inspectors, that Saddam still had an active nuclear weapons program. The Bush administration claimed that the danger of Iraq’s handing off nuclear materiel to terrorists was a key reason for regime change.

The administration knew full well what was stored at Tuwaitha. So how is it possible that the U.S. military failed to secure the nuclear facility until weeks after the war started? This left looters free to ransack the barrels, dump their contents, and sell them to villagers for storage.

How is it possible that, according to Iraqi nuclear scientists, looters are still stealing radioactive isotopes?

The Tuwaitha story makes a mockery of the administration’s vaunted concern with weapons of mass destruction. The U.S. military hastened to secure the Ministry of Oil in Baghdad from looters. But Iraq’s main nuclear facility was apparently not important enough to get similar protection.

The results were unfortunate for the poor villagers in the dun-colored concrete box homes of nearby Mansia, who purchased (or stole) barrels to store water or fuel on their roofs. Some dumped the uranium in their fields; others washed it out with their hands, which they then used for eating. Now they are terrified.

Um Karar, a 40-year-old mother of two in loose blue gown and head scarf, fidgets nervously in her sparsely furnished living room decorated with family photos and plastic flowers. She tells me she sold her barrel back for $3 (in a one-time program organized by the U.S. military that has retrieved about 100 barrels).

“Now we don’t feel anything, but maybe in the future we will be sick,” she says.

Mercifully, experts say such illness is unlikely – unless uranium dust or particles have been ingested, particularly by children. It would be nice if someone were offering to test the villagers.

“Saddam protected us,” says Um Karar in her desperation. “Now there is no security.”

From her roof, I can look just across the road and over a protective fence into “Location C” in Tuwaitha, three buildings in which U.N. weapons inspectors in white protective gear are trying to figure out how many barrels and how much yellowcake – the mixture of uranium oxides that is the product of the uranium extraction process – is missing. The administration didn’t want to let inspectors from the International Atomic Energy Agency back into Iraq. U.S. officials finally recognized, however, that they needed the help of the IAEA which has been monitoring Tuwaitha for years and is best prepared to assess how much uranium is missing.

But the United States is trying to keep the IAEA mission totally under wraps.

The inspectors are kept isolated in the Rashid Hotel and are not allowed to speak to the press. Nor did U.S. officials permit them to bring a press officer from their Vienna headquarters.

When I try to drive toward Location C, where the IAEA team is working on a limited two-week assignment, I am stopped by Sgt. Steven Collier.

Standing in front of a tank, he tells me his superiors “don’t want nobody here right now. They don’t tell us why.”

Maybe U.S. officials are embarrassed. The natural uranium and yellowcake stored at Tuwaitha was not nuclear bomb grade material. But it could be used – if it reached the wrong hands – to make a so-called dirty bomb.

Col. Rick Thomas, a military spokesman, tells me the initial U.S. assessment about the yellowcake dumped out of the barrels was that “none of it was carried away.” Maybe. Maybe not. But why should that option have been left open to terrorists?

And why, in facilities other than Location C, is the looting apparently continuing? Hisham Abdel Malik, a Iraqi nuclear scientist who lives near Tuwaitha and has been inside the complex, told me that in buildings “where there are radioactive isotopes, there is looting every day.” He says the isotopes, which are in bright silver containers, “are sold in the black market or kept in homes.”

According to IAEA spokeswoman Melissa Fleming, such radioactive sources can kill on contact or pollute whole neighborhoods.

How could an administration that had hyped the danger of Saddam handing off nuclear materials to terrorists let Tuwaitha be looted? Maybe the hype was just hype … or maybe the Pentagon didn’t send enough troops to Iraq to do the job right.

Either answer is damning.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.