Troops came in after the facility had been looted
Employees at one of Iraq's main nuclear sites, Al Tuwaitha, have appealed for help after the facility was looted.
Workers say the looters did not appear to be after the uranium, only the containers it was kept in.
But their appeal comes shortly after the UN nuclear watchdog urged the United States to allow it to investigate nuclear sites that have reportedly been looted.
Low-grade uranium was being stored at the Tuwaitha site - a large, sprawling facility about 75 kilometres south of Baghdad.
When Saddam Hussein's regime fell, the guards disappeared and looters poured in.
Employees say the thieves emptied barrels containing low-grade uranium on the ground and then made off to use them to store food and water.
Workers at the site say they then buried the uranium.
One of the facilities chief engineers told the BBC he was concerned about the damage that had already been done.
"The people inside this village, they may die in four months. We need the special teams of radiation, radiation decontamination, decontamination of the area, my village."
There are now American troops at the site - they moved in over the weekend.
But people in and around Al-Tuwaitha say it is too late and they should have been there to stop the looting, the BBC's Caroline Hawley reports.
The IAEA is concerned that radioactive material known to be stored at several Iraqi sites could pose health and environmental risks.
There are also fears they could be used to create a so-called "dirty bomb".
Mohamed ElBaradei - head of the International Atomic Energy Agency - wrote to Washington last Wednesday to request that an investigative team be allowed into Iraq, but has not yet received a response, according to a spokeswoman.
On Monday, State Department spokesman Richard Boucher said Washington was constantly in touch with IAEA on various issues.
But he said "there's no decisions at this point about what role they may or may not play in terms of evaluating and monitoring."
"Coalition forces have secured the facilities that house the natural and low enriched uranium that was at those sites," Mr Boucher said Richard Boucher, said.
"All of this uranium would require significant processing in order to be suitable for enrichment for weapons use."
The IAEA urgently recommended both the Baghdad and Tuwaitha facilities be given protection on 11 April.
It appears US soldiers were sent to some sites but were unwilling or unable to seal them off.
UN chemical and nuclear weapons inspectors - whose relations with the US were soured over abandoned weapons inspections in Iraq - have not so far been allowed to return to Iraq.
But the IAEA is said to have a detailed inventory of radioactive materials at several sites around the country which would help in identifying if such materials have indeed been taken.