Anti-terrorist officers have been granted an extra three days to question six suspected "Real IRA" men.
The suspects were arrested early on Thursday as part of an investigation into an 18-month "Real IRA" bombing campaign in the UK.
Magistrates in London last night granted an extension for officers to continue questioning the six until Monday afternoon.
Under the Terrorism Act, detectives have 48 hours to question suspects but can apply for extensions up to a total of seven days.
The suspects are all aged between 20 and 40 years-of-age and one is thought to be from the Republic of Ireland, while the rest are believed to be from England.
Five were arrested at addresses in London and one in Liverpool. Officers and an Army bomb squad also searched an unused pig farm at West Ardsley, near Leeds, as part of the inquiry.
About 20 neighbouring residents were evacuated as a series of controlled explosions were carried out on the farm.
The locals spent Thursday night in a nearby community centre but were allowed to return home last night after the tight cordon was lifted. The local school, Hill Top Infants School, was also closed.
In a statement yesterday morning, Assistant Chief Constable Grahame Maxwell said: "Yesterday West Yorkshire Police executed two search warrants under the Terrorism Act in the West Ardsley area of Leeds. These searches were conducted by the Metropolitan Police.
"Acting on safety advice from the Army bomb disposal unit, some residents were evacuated from their houses and local roads were cordoned off."
Mr Maxwell said it had been a "difficult operation" but that officers' priority was to ensure the safety of the community.
A Metropolitan Police spokesman later said that anti-terrorist branch officers were no longer at the West Ardsley farm, suggesting the operation in that area had ended.
PA