Iraq is searching for potentially deadly radioactive material that was stolen late last year, officials said.
The material was contained in an industrial radiography device that vanished in November, the International Atomic Energy Agency (IAEA) told NBC News on Wednesday. Its disappearance has raised fears the material could fall into the hands of ISIS fighters who control parts of the country.
An Iraqi environment ministry document seen by NBC News also confirmed the reported theft from a storage facility linked to Weatherford, a U.S. oilfield services company.
The IAEA said the missing "Ir-192 radioactive source in a shielding container" was classified as a Category 2 radioactive substance that, if not managed properly, could be fatal to someone exposed for a period of hours to days.
It was stolen in the southern city of al-Zubair, which is more than 300 miles south of the nearest area fully controlled by ISIS. However, the terrorist group has claimed attacks there — including one that killed 10 people in October in the district where the facility is located.
The State Department said it was aware of the reports and was monitoring the situation. However, spokesman Mark Toner said it had "not seen any indication that the material in question is being acquired by [ISIS] or any other terrorist group in the region."
He added: "Based on the information provided, we can't speculate on the suitability of the material for use in, say, a dirty bomb."
A senior Iraqi security official said searches of the area had been conducted but no trace of the material has been found.
"The material was stolen in mysterious circumstances," the official said. "If ISIS militants have the capabilities to turn this material into a weapon, or to use it to help them to manufacture a weapon, this could be so dangerous."
Bushra Ali, director of the Iraqi Radiation Protection Center, said: "This is a dangerous material if it is used by people who do not know how to deal with it. It is the duty of the security authorities to know the capabilities of the people who took it, who can turn it into a deadly weapon."
The IAEA said it offered assistance to Iraqi authorities but none had been requested so far.
The radioactive material could cause harm simply by being left exposed in a public place for several days, David Albright, a physicist and president of the Washington-based Institute for Science and International Security, told Reuters.
"If they left it in some crowded place, that would be more of the risk, if they kept it together but without shielding," he said. "Certainly it's not insignificant. You could cause some panic with this. They would want to get this back."
However, IAEA guidelines [PDF link here] note that Category 2 material stored correctly would be "very unlikely" to permanently injure or be life-threatening to people nearby. "There would be little or no risk of immediate health effects to persons beyond [110 yards] or so away, but contaminated areas would need to be cleaned up," it notes.
In a statement from its operational headquarters in Houston, Texas, Weatherford referred enquiries to another company, SGS.
"Weatherford has no responsibility or liability in relation to this matter because we do not own, operate or control sources or the bunker where the sources are stored," said a statement from corporate communications manager, Kelley Hughes.
SGS could not immediately be reached for comment from NBC News.