A woman has been arrested in connection with a police raid at a bar in the Tiger's Bay area of north Belfast.
Police wearing gas masks returned to search the bar
Seventeen men who were arrested during the raid at the Alexandra Bar on Thursday are being held under the Terrorism Act.
The men are being questioned about membership of a banned organisation and having items of use to terrorism.
Detective Superintendent Roy McComb said the raid was aimed at the Ulster Freedom Fighters.
He said were acting on information suggesting a rehearsal for a "show of strength" was in progress.
He said tactics - which included firing CS gas pellets into the bar - were used in the belief that the men were armed.
"Information presented itself that members of an illegal organisation with illegal firearms were going to present themselves as some sort of defenders of the people," Mr McComb said.
It is believed that half of those arrested were dressed in combat style uniform, but police have not yet revealed if anything, including weapons, were retrieved from the bar.
A full-scale search continued on Friday with police officers coming and going from the pub wearing gas masks.
The UFF is part of the Ulster Defence Association, set up as its "military wing" before the UDA was proscribed.
The police operation began just before 2000 GMT on Thursday.
Bar doors were ripped off their hinges and some upstairs windows in the bar were smashed during the raid.
It is understood that one of those arrested is already facing terrorism-related charges.