A man is being questioned by PSNI officers today about the discovery of incendiary devices linked to dissident republicans in Northern Ireland.
He was arrested in the Co Tyrone village of Sion Mills, just outside Strabane, where a number of devices were found last week.
One of four men held in an earlier operation was later charged.
A house in Sion Mills was also searched as part of today's security operation, police said.
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Dissident republicans are suspected for a number of firebomb attacks on members of the District Policing Boards in the area.