Four men are being held in connection with a series of arson attacks in Co Donegal.
Five men, aged between 17 and 24, were arrested yesterday as part of the investigation into 11 fires in the Buncrana area since early July.
Properties including farm buildings, vehicles and a health centre have all been targeted in what gardaí describe as random attacks.
The 17-year-old was released last night.
The other four men are being detained at Buncrana and Letterkenny Garda Stations.
