A stash of "highly dangerous" radioactive material has been stolen from Iraq sparking fears it could fall into the hands of ISIS.
The substance was stolen last year, and along with similar disappearances from the US, Britain and other countries, worries are growing Islamic State could create a dirty bomb.
But could the terror group use the material to make a nuclear bomb?
A dirty bomb combines nuclear material with conventional explosives to contaminate an area with radiation.
But this is in contrast to a nuclear weapon, which uses nuclear fission to trigger a vastly more powerful blast.
"We are afraid the radioactive element will fall into the hands of Daesh," said a senior security official with knowledge of the theft.
"They could simply attach it to explosives to make a dirty bomb," said the official, who works at the interior ministry and spoke on condition of anonymity as he is also not authorised to speak publicly.
The material, stored in a protective case the size of a laptop computer, went missing in November from a storage facility near the southern city of Basra belonging to U.S. oilfield services company Weatherford, the document obtained by Reuters showed and officials confirmed.
A document, dated November 30 and addressed to the ministry's Centre for Prevention of Radiation, describes "the theft of a highly dangerous radioactive source of Ir-192 with highly radioactive activity belonging to SGS from a depot belonging to U.S. oilfield services company Weatherford, the document obtained by Reuters showed and officials confirmed.
The material is classed as a Category 2 radioactive source by the International Atomic Energy Agency, meaning if not managed properly it could cause permanent injury to a person in close proximity to it for minutes or hours, and could be fatal to someone exposed for a period of hours to days.
How harmful exposure can be is determined by a number of factors such as the material's strength and age, which Reuters could not immediately determine.
The ministry document said it posed a risk of bodily and environmental harm as well as a national security threat.
There was no indication the material had come into the possession of Islamic State, which seized territory in Iraq and Syria in 2014 but does not control areas near Basra.
A spokesman for Basra operations command, responsible for security in Basra province, said army, police and intelligence forces were working "day and night" to locate the material.
Besides the risk of a dirty bomb, the radioactive material could cause harm simply by being left exposed in a public place for several days, said David Albright, a physicist and president of the Washington-based Institute for Science and International Security.
"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."
The senior environmental official said authorities were worried that whoever stole the material would mishandle it, leading to radioactive pollution of "catastrophic proportions".