Fears of a revenge attack following Osama Bin Laden’s killing increased last night after five men were arrested under the Terrorism Act close to the Sellafield nuclear site.
The suspects, all in their twenties and from London, were detained by armed police hours after Britain was placed on red alert for possible reprisals after the Al Qaeda leader’s death.
They had driven 300 miles to the site, which has long been regarded as a major target for Islamic terrorists.
Held: The five men, all in their 20s and from London, were arrested under the Terrorism Act and held in police custody before being taken to Manchester yesterday morning
Police became suspicious after the men, of Bangladeshi origin, were seen taking photos near Sellafield, which handles dangerous nuclear material.
Four houses in Romford, East London, were being searched by counter-terror detectives last night. Immigration officials were checking whether the men were in Britain lawfully.
Scotland Yard revealed that a suspicious container was removed from one of the London addresses. Initial tests revealed it did not contain explosives but as a precaution it was taken away for further tests.
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Security sources said there had been ‘strong grounds’ to detain the men because of their suspicious behaviour and the ‘dubious’ explanation they gave for their trip.
Their arrests came hours after the announcement Osama bin Laden had been killed in Pakistan during a secret U.S. raid.
There have been warnings across the world that the assassination could spark a wave of terror attacks in retaliation but police said they are not aware of any connection at this stage with the arrests in Sellafield.
A statement from Cumbria Police said: 'At 4.32pm yesterday, Monday 2 May, police officers from the Civil Nuclear Constabulary conducted a stop check on a vehicle close to the Sellafield site in West Cumbria.
'As a result, police officers from Cumbria Constabulary arrested five men from London, all aged in their 20s, under Section 41 of the Terrorism Act.
'They were taken to police custody in Carlisle overnight and are being transported to Manchester this morning.
'The investigation is being led by the North West Counter Terrorism Unit. A road closure affected the area for a short period of time.'
Both the location and timing of yesterday's incident will cause concern. The terror arrests came outside the Sellafield site, which handles highly dangerous nuclear material.
They were also made in an apparent vehicle stop check within hours of the news breaking that Bin Laden had been killed.
Greater Manchester Police said the investigation was in its early stages. A spokesman said: 'At this stage, we are not aware of any connection to recent events in Pakistan.'
Section 41 of the Terrorism Act 2000 allows a police officer to arrest any person whom he 'reasonably suspects' to be a terrorist.
The sprawling Sellafield site on the Cumbrian coast is heavily protected by both private security and officers from the Civil Nuclear Constabulary, some of whom are armed.
Sellafield is responsible for decommissioning and reprocessing nuclear waste and fuel manufacturing, on behalf of the Nuclear Decommissioning Authority.
The Sellafield site has been operational since the 1940s, when it was used as a Royal Ordnance factory supporting the war effort. The site is also home to the world's first commercial nuclear power station - Calder Hall, which operated from 1956 to 2003.
Today the site comprises a wide range of nuclear facilities, including redundant facilities associated with early defence work, as well as operating facilities associated with the Magnox reprocessing programme, the Thermal Oxide Reprocessing Plant, the Sellafield Mox plant and a range of waste treatment plants.
Manchester Police would not be drawn on whether the suspects were Asian or how close they were to the Sellafield site.
The arrests are not believed to have been intelligence-led. A source suggested the suspects may have been taking photographs.
Scotland Yard counter-terror detectives are 'making inquiries' to help GMP with its investigation.
David Cameron said yesterday that Bin Laden’s death would be ‘welcomed right across our country’.
But security was stepped up as he warned: ‘It does not mark the end of the threat we face from extremist terrorism. Indeed, we will have to be particularly vigilant in the weeks ahead.’
Secret information revealed by WikiLeaks last week detailed threats from a terror suspect interrogated at Guantanamo Bay who spoke of Al Qaeda unleashing a 'nuclear hellstorm' on the West if Bin Laden was ever captured or killed.
Last night the Prime Minister chaired a meeting of the Government’s emergency planning committee Cobra to assess the implications for the UK. Security sources have been told of specific threats against targets in North Africa and Europe.
Officials in Britain fear a ‘lone wolf’ - currently off the security services’ radar - could be inspired to take revenge.
There is no specific intelligence pointing to any attack in response to Bin Laden’s death, but it is ‘common sense’ to be on guard, Whitehall officials say.
Possible targets include popular tourist and business locations including the Houses of Parliament, Canary Wharf and the London Eye, say security experts.
Labour leader Ed Miliband declined to comment directly on the arrests but said: 'It is right that the Government has stepped up security at various places and obviously they will act on any intelligence they have.'
A spokesman at Sellafield said the site - the largest nuclear facility in Europe - was 'operating as normal'.
Britain's terror alert level is currently as 'severe', which means a strike is 'highly likely' but no sprecific threat is known of.