A man in his 60s has been arrested under terrorism laws following the discovery of uranium at Heathrow Airport last month.
A small amount of uranium was found in a shipment of scrap metal on 29 December, although it was not reported until last week.
The shipment came from Pakistan, via Oman on an Oman Air passenger flight.
Police said the man was arrested in Cheshire on Saturday and has been released on bail until a date in April.
Officers did not find any other dangerous material at the address in Cheshire but the offence the man was arrested for relates to the making or possession of radioactive material, Sky News reports.
Metropolitan Police Commander Richard Smith, who leads the force’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.”
The man has been released on bail until a date in April.