United Nations, Oct 28 : Mohamed ElBaradei, the chief of the International Atomic Energy Agency, has said in a speech that the number of reports of nuclear or radioactive material stolen around the world last year was "disturbingly high."
Dr. ElBaradei, in his annual report on Monday to the General Assembly, said nearly 250 such thefts were reported in the year ending in June.
"The possibility of terrorists obtaining nuclear or other radioactive material remains a grave threat. Equally troubling is the fact that much of this material is not subsequently recovered," The New York Times quoted him, as saying.
Members of Dr. ElBaradei's staff and outside experts cautioned that the amount of missing material remained relatively small. If all the stolen material were lumped together, it would not be enough to build even one nuclear device, they said.
It is also unclear if the rising number of reports of stolen material stems from a growing market for radioactive goods or more vigilant reporting of thefts by member states.
However, the idea that there might be a new market for such material is of concern, they said, especially if some of it were to end up in a dirty bomb.
The threat from such a bomb is less a health risk from radiation than from the panic an attack would probably cause, said Cristina Hansell, a professor at the Center for Nonproliferation Studies, in Monterey, Calif.
Most of the concern about thefts centers on the countries of the former Soviet Union, where nuclear programs were widespread, but they occur everywhere.
In a typical case, Hansell said, an oil company reported last May that a device containing radioactive material that was used in exploration in Sudan was missing.
It would take long exposure to the device to create any health risk, she said.
Aside from the issue of thefts, Dr. ElBaradei said he hoped that North Korea, which left the Nuclear Nonproliferation Treaty in 2003, would return, and he criticized Iran for impeding the agency's attempts to verify whether it was developing nuclear weapons.