The United Nations nuclear watchdog has accounted for most of the uranium feared stolen from Iraq's largest nuclear site, Tuwaitha, reports say.
US soldiers delayed sealing the site even after weeks of looting
The prestigious US-based journal Science said inspectors had found virtually all the missing material, quoting an unnamed official from the International Atomic Energy Agency (IAEA).
There has been no official comment.
Separately US President George W Bush said looting could be one of the reasons why the former Iraqi regime's suspected arsenal of weapons of mass destruction has not yet been found.
"For more than a decade, Saddam Hussein went to great lengths to hide his weapons from the world," Mr Bush said in his weekly radio address.
"And in the regime's final days, documents and suspected weapons sites were looted and burned."
IAEA spokeswoman Melissa Fleming told BBC News Online that a team of IAEA inspectors which began visiting the Tuwaitha facility earlier this month was continuing its work.
The seven-member team is checking nuclear material against the agency's inventories.
They are expected to report by the end of next week.
Tuwaitha was heavily looted for a period during the war, and there has been particular concern about barrels which once stored low-enriched uranium, known as "yellow cake".
The barrels were emptied and sold to local people for $2 each by looters. Many used the barrels to hold drinking water or food, or to wash clothes.
About 1.8 metric tons of "yellow cake" and 500 tons of unrefined uranium went missing as the Iraqis left Tuwaitha unattended during the war.
Although an estimated 20% of the containers which stored the uranium were taken from the site, it appeared that looters had dumped the uranium before taking the barrels.
Much of it appears to have been on or near Tuwaitha, unnamed diplomats said, quoted by the Associated Press news agency.
The IAEA team is visiting the Tuwaitha site, which is 50 kilometres (30 miles) south of Baghdad, under close American guard.
The IAEA's Mohamed ElBaradei warned that Iraq could face nuclear contamination
The visit was agreed after weeks of pleading by the IAEA, which has kept the radiological materials at the site safely under UN seal for 12 years.
However, members of the UN group - all non-Americans, with expertise ranging from nuclear physics to arms-control analysis - are not authorised to look at issues of health and safety arising from, for example, the misuse of the barrels.
In preparation for the visit, the Americans ordered villagers to sell back the barrels for $3 each. The Pentagon says it has so far received about 100 of the 3,000 missing barrels.