A 21-year-old man was arrested on suspicion of holding documents that could be useful to a terrorist.
The arrest in York was part of an operation planned by the Northeast counter-terrorism police.
A bomb disposal unit was called during a search of a property in the Boroughbridge Road area of the city, officials said.
Numerous residents were evacuated for a short period.
The arrested man remains in custody, while the streets in the area have been reopened and a cordon has been raised.
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