Police have been granted another week to question five people, including a 16-year-old boy, arrested on suspicion of right-wing terrorism offences.
Officers carried out a series of raids in West Yorkshire, Swindon and Anglesey in Wales on Saturday.
Counter Terrorism Policing North East said they had gained a warrant of further detention for those arrested.
The extension gives officers until 8 May to charge or release them or to apply for an additional extension.
Police said two men, aged 29 and 30, and a 28-year-old woman had been arrested in Keighley, West Yorkshire, on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism.
A 16-year-old boy was arrested in Swindon and a 28-year-old man was arrested in Anglesey on suspicion of the same offence.
All five were taken to a police station in West Yorkshire for questioning.
A Counter Terrorism Policing North East spokesperson said the arrests formed part of an ongoing investigation into right-wing terrorism.