Two men being questioned about dissident republican activity have been released unconditionally.
The men, aged 41 and 47, were arrested in Strabane on Friday.
Five other people arrested on Saturday - four men and a woman ranging in age from 33 to 46 - are still being questioned.
Police carried out searches in Toome, County Antrim, and Carrickmore, Cookstown, Omagh and Pomeroy in County Tyrone.
A number of cars were seized during the searches.
The five people were taken to Antrim PSNI station for questioning.