WASHINGTON – A team from the International Atomic Energy Agency is on the ground in Nigeria for what it describes as a “radiological emergency.”

Sources say radioactive material was stolen from a Nigerian oil company.

The Nigerian Nuclear Regulatory Agency admitted earlier this week that devices used to X-ray oil pipelines for cracks were “lost.”

But sources tell Fox News that officials now believe the disappearance of the material was a “strategic theft.”

Officials will not specify how much material was stolen, but they say it’s a significant amount of americium and beryllium # radioactive elements that could be used to make a “dirty bomb.”

Officials could not say whether the radioactive material may have been transported out of the country.

Defense and U.S. intelligence officials say many African countries provide safe-haven for terrorist cells, and that Nigeria may be one of them.