Police have refused to comment on reports that a man being questioned under the Official Secrets Act tried to pass military secrets to the Russians.
A 23-year-old man has been charged with possessing explosives.
The unnamed man, who is in his 20s, was detained on Wednesday in Leeds, and a domestic and a business property have been searched in Skipton, North Yorks.
Peter Stephen Hill, a risk analyst, from Skipton, North Yorks, was charged under the Explosive Substances Act and will appear in court on Monday.
Scotland Yard said it could not comment on the reported connection to Russia.
He was detained on Wednesday in Leeds by Metropolitan Police officers and a domestic and a business property were searched in Skipton.
But it has emerged that the team of officers is brought in only over matters of national security.
Scotland Yard said it could not confirm claims he was also questioned under the Official Secrets Act.
The arrest comes just days after MI5 said Russia and China were spying on the UK.
But it emerged that a specialist team of officers is brought in only over matters of national security.
In a speech, MI5 director general Jonathan Evans said it was a matter of "some disappointment" that the service was still having to deal with "unreconstructed attempts" at spying by these countries.
The Metropolitan Police said the man would appear in custody at Leeds Magistrates' Court on Monday.
The Metropolitan Police said the man had been arrested under both the Official Secrets Act and the Explosive Substances Act.
The Yorkshire Post reported the man was originally arrested under the Official Secrets Act, for allegedly attempting to pass military information to Russia.
In a statement, it said: "Following an application to court for an extension of custody the man remains in custody at a Yorkshire police station."
The paper said the breach of security was related to a government rather than a commercial source.
The Yorkshire Post reported that the arrested man is 23, thought to be British, and recently moved to the Skipton area.
The paper said the alleged breach of security was related to a government rather than a commercial source.