A Skipton man is being questioned by officers from the Metropolitan Police's Counter Terrorism Unit after swoops on three addresses.
The man, in his 20s, was arrested under the Official Secrets Act at business premises in Leeds on Wednesday night.
He was then further arrested under the Explosive Substances Act of 1883 following searches of his home and another business address, both in Skipton.
The suspect was tonight being questioned at an undisclosed police station in West Yorkshire after officers were granted an extension by magistrates to keep him in custody until tomorrow night.
The West Yorkshire and North Yorkshire forces were informed of the Metropolitan Police investigation and supported them with the searches.
It is understood that, though some type of material was found during the searches which led to the man's arrest under the Explosive Substances Act, he is being questioned by Counter Terrorism officers who specialise in Official Secrets offences.
Last night the search of the business premises in Skipton was ongoing, but officers had completed the search of the residential property.
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