A man has been arrested on suspicion of a terror offence after traces of uranium were found at Heathrow Airport last month.
A small amount of the radioactive material was found on December 29 during the routine screening of a package found with a shipment of scrap metal that reportedly originated in Pakistan and arrived on a flight from Oman.
Police said a man, in his 60s, was arrested on Saturday morning on suspicion of a terror offence at an address in Cheshire and has now been released on bail.
Officers searched the man’s address but no material that was a threat to the public was found, the force said.
Commander Richard Smith, who leads the Met’s Counter Terrorism Command, said: “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 inquiry available to us, which has led us to making this arrest over the weekend.
“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.”
On Wednesday, 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 that people should be reassured that the substance 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.”
Additional reporting by PA