A man was arrested at John F. Kennedy Airport on Wednesday with raw uranium inside the soles of shoes carried in his luggage, and officials believe he was planning to ship the radioactive element to Iran.

According to a federal complaint obtained by the Smoking Gun, Patrick Campbell, a 33-year-old native of Sierra Leone, has been under investigation by the Department of Homeland Security for the past 15 months, and allegedly agreed to sell undercover agents 1000 tons of yellowcake uranium for shipment to Iran.

Campbell had reportedly flown from Paris to Ne York, and was stopped at JFK; he was supposed to catch a connecting flight to Miami, where agents planned to meet up with him. The complaint notes that Campbell was found with raw uranium ore in the soles of two pairs of shoes, in addition to a thumb drive containing a contract for the sale and delivery of more uranium.

Though the amount of uranium Campbell brought with him into the United States is not believed to be harmful, processed yellowcake uranium can be further processed into nuclear weapons. He has been charged with violating the International Emergency Economic Powers Act and the Iranian Transaction Regulations, and faces up to 20 years in prison, along with a possible $1 million fine, if convicted.