Five terror suspects are being questioned by detectives after being arrested outside the Sellafield nuclear plant in Cumbria.
Counter-terror police also raided four houses in east London linked to the suspects, who were held after a vehicle stop-check near one of the UK's most sensitive nuclear installations.
A police spokesman would not be drawn on reports the suspects had been filming the Sellafield site and are all Bangladeshi.
The gang of five men, all in their 20s and from London, were held on Monday afternoon, 300 miles from their homes, and just hours after news broke of the killing of Osama bin Laden in a raid by US special forces in Pakistan.
It put the Western world on high alert of possible revenge attacks from al Qaida, amid threats of a "nuclear hellstorm" on the West if bin Laden was ever captured or killed.
The suspects were detained at 4.32pm following a stop check on their vehicle by officers from the Civil Nuclear Constabulary, which polices the vast Sellafield site in West Cumbria.
The five were then arrested under the Terrorism Act by officers from Cumbria Police, held in custody in Carlisle overnight and transferred to Manchester to be dealt with by the North West Counter Terrorism Unit, based in the city.
After details of the arrests were released by the Cumbria force and Greater Manchester Police, Scotland Yard released details of the raids on four houses in east London.
The Metropolitan Police confirmed the raids formed part of the investigations into the men held at Sellafield, following information passed to them by GMP.
The arrests are not believed to have been intelligence-led, but as a direct result of the initial police stop check on the suspects' vehicle.