British police added that it did not appear to be linked to any direct threat or any public health threat.
The amount of radioactive material, detected by routine scanning on Dec. 29, was extremely small and had been assessed by experts as posing no risk, Richard Smith, head of London police's Counter Terrorism Command said.
"We were relieved to understand there was no threat to public health or public safety," Smith told the London Assembly. "The consignment that had been identified included a very small amount of contaminated material. We are now conducting further inquiries."
He said the key message was that the airport screening operation had functioned as it should. Police said no arrests had been made.
Heathrow Airport declined to comment and referred enquiries to the police, Reuters reported.
Uranium can be used for civilian power generation and scientific purposes and is a key ingredient in nuclear weapons. Certain isotopes emit radiation that can be harmful to humans, and the metal itself is toxic if ingested or inhaled.
MP/PR