A man has been arrested on suspicion of a terror offence after traces of uranium were found at Heathrow Airport last month.
Scotland Yard confirmed the suspect, in his 60s, was arrested in connection to incident on December 29.
Counter terror-cops had earlier confirmed Met Counter Terrorism Command officers were contacted by Border Force from the airport when a material was found to be contaminated during a "routine screening".
The constabulary has reassured that the "extremely small" amount discovered poses "no threat".
Police in Cheshire detained the suspect on Saturday under Section nine of the Terrorism Act and he has been bailed until April.
Commander Richard Smith, who leads the Met's Counter Terrorism Command, said: "I want to be clear that despite making this arrest, and based on what we currently know, this incident still does not appear to be linked to any direct threat to the public.
"However, detectives are continuing with their inquiries to ensure this is definitely the case."
Border Force officers found the radioactive material with a shipment of scrap metal on December 29.
At the time it was reported to have originated in Pakistan and was bound for Iranians in the UK.