A man has been arrested under terrorism laws after traces of uranium were found in a cargo package at Heathrow Airport, police said.
Border Force officers found the radioactive material with a shipment of scrap metal on December 29 which, according to the Sun newspaper, had originated in Pakistan and was bound for Iranians in the UK.
Police in Cheshire detained the man, in his 60s, on Saturday under Section nine of the Terrorism Act.
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.”
Officers said they did not find any other dangerous material at the address in Cheshire but the offence the man is accused of relates to the making or possession of radioactive material.
A spokesperson from the Met said the uranium was found during “routine screening” at Heathrow.
Mr Smith added: “The discovery of what was a very small amount of uranium within a package at Heathrow Airport is clearly of concern, but it shows the effectiveness of the procedures and checks in place with our partners to detect this type of material.
“Our priority since launching our investigation has been to ensure that there is no linked direct threat to the public. To this end, we are following every possible line of enquiry available to us, which has led us to making this arrest over the weekend.”
Colonel Hamish de Bretton-Gordon, a chemical and biological weapons expert and former head of the UK’s nuclear defence regiment, told the BBC Radio 4 Today programme on Wednesday that people should be reassured that it was detected.
He said: “It’s very clear that the comprehensive surveillance network that we have in place in this country, run by the security services, the police and others, has actually worked and picked up potentially a very dangerous containment that could provide a threat.
“In this country I think people should be pretty reassured that we’re not going to see dirty bombs from this type of material.”
Asked what could have happened to the metal, he said: “If it is for nefarious reasons, for bad reasons, to create mayhem by Iranians or some sort of Russian proxy, then that is an area of concern.
“But I think the key thing is that there are people looking out for this and this should not worry the public unduly.”