Two men and a woman have been arrested in Keighley and two properties in the town are being searched as part of an investigation into suspected right-wing terrorism.
Officers say a 29 year old man, a 30 year old man and a 28 year old woman have all been arrested on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism under section 41 of the Terrorism Act 2000.
As part of the same pre-planned operation, a 16 year old boy was arrested in Swindon, Wiltshire and a 28 year old man was arrested in Anglesey, North Wales.
All five have been taken to a police station in West Yorkshire for questioning.
The arrests form part of an ongoing investigation led by Counter Terrorism Policing North East into right-wing terrorism.
Following the discovery of potentially suspicious material at one of the addresses - on Braithwaite Drive in Keighley - the Explosive Ordnance Disposal Unit (EOD) was called to provide specialist advice and to arrange the safe removal of the items if required.
As a precautionary measure, a cordon has been put in place and a number of local homes have been evacuated whilst examinations are conducted.
A spokesperson said: "We recognise that local people may have concerns as a result of this activity. We would like to reassure them that these arrests are pre-planned and intelligence led and there is not believed to be any immediate risk to the local community. We are grateful for the understanding, patience and support of local residents while these enquiries continue."
Update at 9.15pm Saturday 1st May:
Police say the cordon around properties in Keighley has now been removed and residents are permitted to return to their homes.
Officer say they are grateful for residents’ patience and understanding, and apologise for the unavoidable disruption.
The five individuals arrested this morning remain in custody at this time. Enquiries are ongoing.