The arrests come amid fears of revenge attacks by terrorists after Osama Bin Laden's reported death in Pakistan on Sunday night.
The men who in their twenties, all hail from London and were arrested shortly after the news of Bin Laden's death on Monday (2).
Civil Nuclear Constabulary officers conducted a stop check on a vehicle close to the nuclear plant in the Sellafield site. The suspected men appeared to have been taking pictures after being arrested under the Terrorism Act, although the arrest was not intelligence led.
In a statement, Greater Manchester Police (GMP) said: "At this stage we are not aware of any connection to recent events in Pakistan."
A GMP spokesman said the investigation is in its early stages and no further information will be released yet.
A police officer can arrest anyone they "reasonably suspect" of being a terrorist, under Section 41 of the Terrorism Act 2000.
As part of the investigation four houses in east London were raided by counter-terror detectives. A small container was removed at one of the addresses and is being examined by Scotland Yard. After examination by explosives officers, the container is now not thought to have had any hazardous material.
Scotland Yard said: "The Met continue to urge the public to remain vigilant and be aware and to report any suspicious behaviour which may be terrorist-related.
“The threat level to the UK remains unchanged at severe, which means that an attack is highly likely.”
